by Vicente Pecoraro

The skin is an organ extended on the surface. The complex structures that constitute it, derived from the ectoderm and mesoderm, its extension of about two square meters, its topographic situation that connects and that at the same time separates the organism from the environment, its important functions, some of its own and others shared with other structures of the organism (for example, the maintenance of homeostasis), presume the richness and heterogeneity of its pathology.

Anatomy and physiology

The skin comprises three superimposed layers: the epidermis, of ectodermal origin, and the dermis and hypodermis, or subcutaneous cellular tissue, of mesodermal origin. The cell unit of the epidermis is constituted by the basal cell or keratinocyte, which forms the deep, basal layer, and from which the rest will derive. The keratinocyte, as it matures and evolves towards the surface, becomes the mucous body of Malpighi. The cells of this stratum, the most important of all, since most of the pathological processes of the skin are located there, are joined together by special structures called desmosomes. Next, the granular layer appears, derived from the maturation of the mucous body; This maturation process ends with the formation of the horny layer or stratum disjuntum. This layer reflects the alterations produced on the progenitor layers. In palms and plants, a fifth layer is observed, the stratum lucidum, located between the last two mentioned above.

From the functional point of view, two other layers called epicutaneous must be added, which lack anatomical individuality because their constitution is largely physicochemical. They are: a) the emulsified layer constituted by the lipids of the sebaceous secretion, by the water contributed by the sweat and by the "insensitive perspiration", resulting from the metabolism of the epidermal cells; b) the gaseous layer, formed by the air that surrounds the skin, with a thickness of approximately 6 mm, comparable to the atmosphere that surrounds the earth, but more humid, hot, and with a higher carbon dioxide tension.

Forming part of the epidermis are three cell types of a different lineage than keratinocytes: the melanocyte, the Langerhans cell and the Merkel cell. The first two regularly integrate the cellularity of the epidermis and, although they can be found in other sectors of the body, they maintain a harmonious functional relationship with the former. The melanocyte - derived from the neural crest - produces melanin, which gives the skin its special pigmentation, which protects it from ultraviolet radiation; It is distributed following a structural ordering and a functional association with the keratinocyte, which makes it possible to recognize an epidermomelanic unit, since each melanocyte is related to a constant population of keratinocytes. Langerhans cells are assumed to have their origin in the bone marrow; Thus, They can be found in the ganglia and other viscera, but due to their positive epidermotropism, some migrate towards the epidermis. Their particular morphology, with the special granulations they contain (Birbek granules), allows them to be identified. Their functions are not fully known, but they are known to play an important role from an immunological point of view.

With respect to the Merkel cell, possibly also derived from the neural crest, it is a mechanoreceptor.

The dermoepidermal junction shows a scalloped outline due to the presence of extensions of the epidermis: the epidermal ridges. At this level, the presence of the basement membrane is observed, arranged parallel to the plasma membrane of the basal cells, with their hemidesmosomes. Both layers participate in the constitution of this complex membrane. The union of the epidermis with the dermis is completed by a series of walking fibrils and microfibrils, which are in contact with the collagen fibers of the superficial dermis.

The dermis, from which the epidermis feeds, is made up of cells and fibers. The cells, normally few in number, are fibroblasts, mast cells, macrophage histiocytes, and some cells of blood origin, such as lymphocytes and granulocytes.

The most important of these cellular elements, due to the functions they fulfill, are fibroblasts and mast cells, especially. The fibers are of three types: collagen, elastic and reticulin. Both fibers and cells are embedded in the ground substance.

The dermis comprises two layers: the superficial or papillary, which also has a scalloped contour due to the presence of elevations, the dermal papillae, which alternate with the epidermal ridges, while below is the reticular dermis, characterized by the existence thick bands of horizontally oriented fibers and few fibrocytes. The scalloped contour of the dermoepidermal junction determines the formation, on the surface of the palmar and plantar epidermis, of a series of elevations and grooves or depressions that constitute what is called the dermatoglyphic. Its distribution is so particular and selective for each individual that its study makes it a first-order method for the identification of the subject. Likewise, and from a medical point of view,

Underneath the dermis and closely related, is the hypodermis or subcutaneous cellular tissue, whose elemental cell unit is constituted by the fat, lipocyte or adipocyte cell.

The skin is endowed with a series of structures called skin appendages or annexes. They are: a) the hair, which together with the sebaceous gland and the erector hair muscle constitute the hair follicle or pilosebaceous unit; b) nails, which are keratinized structures, located at the distal end of the fingers, and which fulfill a protective function; e) the eccrine and apocrine sweat glands which, together with the sebaceous ones, are destined to fulfill important secretory functions.

The presence or absence of hair follicles allows us to distinguish two areas of human skin: a) glabrous skin, without hair follicles, such as that of the palms and soles and semi-mucous membranes, and b) the rest of the integument, populated by hair follicles; These can produce terminal hair of variable length, usually thick and pigmented (scalp, beard, mustache, pubis, armpits) or hair with opposite characteristics to the previous one, but which, under pathological conditions, can become terminal hair ( hypertrichosis in men, hirsutism in women).

Other anatomical aspects of importance must be consigned. The skin is endowed with a wide capillary vascular network, located below the epidermis, which is arranged in two plexuses: the superficial or subpapillary and the deep or subdermal, which especially irrigate the hypodermis. From both plexuses emerge the vessels that supply the appendages and the capillary loops that are located in the papillae. The drainage is made by venules and lymphatics of centripetal circulation.

The skin is endowed with a series of nerves and sensory organs. It is, without a doubt, the most widespread organ of the senses and keeps the body informed of all environmental stimuli. It is made up of centrifugal fillets that belong to the autonomic nervous system (ortho and parasympathetic), which fulfill vasomotor and secretory functions, and fundamentally by centripetal and sensory cerebrospinal nerves that ensure the sensory functions of the skin. In addition, in the dermis, especially, and in the hypodermis, a series of corpuscles are housed that would react specifically to certain stimuli.

The Wagner-Meissner, Merkel-Ranvier, Krause and Ruffmi corpuscles, located in the dermis, and those of Vater-Pacini, in the hypodermis, are classically described. They would be, respectively, the receptors of tactile sensitivity (the first two), heat, cold and pressure.

Some authors affirm that this differentiation has no place at the moment, since they consider that any of them could be a recipient of all the aforementioned stimuli, with the exception of the Vater-Pacini corpuscles, which would continue to be related to pressure sensitivity. But the facts confer a certain relativity to this conception, taking into account its special location; In other words, if their function were limited to the one assigned to them, obviously, they should also be present outside of them, and furthermore, their number should be higher. Some facts support this way of thinking: you can feel cold during times of fear and anxiety; chills accompanying feverish states and a feeling of heat in moments of anger or other states of tension, and all this occurs without changes in ambient temperature. It is true that, in these cases, the role that vasomotor alterations could play, that is, the vascular constriction and dilation that accompany these states, cannot be ignored.

The skin has a constitutive (constitutional) color and an induced color. The normal coloration of the skin depends on many factors among which the genetics occupy the first place. According to the racial type -caucasoid, Negroid, etc.- it can be white, brown or black. In our environment the white color prevails, that is, that of the Caucasus. In them, the color of the skin is determined by the thickness of the horny layer, the number of blood vessels, related to the state of hemoglobin, oxygenated or reduced, of the blood it contains, by melanin and, to a lesser degree, by carotenoids. As regards melanin, the intensity of its coloration is subject to variations subordinate to the greater or lesser exposure of the skin to solar radiation. The term etiolation defines the pallor of the skin typical of subjects who are not exposed to sunlight (miners, nocturnal individuals). Normally, the color can vary due to factors that determine vasodilation or vasoconstriction, environmental, climatic, and psychic stimuli, etc. Consequently, the causes that modify the color can be grouped into vascular, pigmentary and of various etiologies.

Functions of the skin

The functions that the skin fulfills to defend itself and at the same time defend the organism are multiple: a) functions of keratogenesis, sweating, sebogenesis and melanogenesis, and b) functions of homeostasis. It is evident that the skin plays an important protective function of the body, regulating the entry and exit of substances with which it is in permanent contact and preventing dryness and mummification of the underlying tissues. It is highly resistant to trauma, low irritability, extraordinary elasticity and a high threshold of sensitivity to infection.

The skin constitutes a humoral and cellular defense mechanism, as evidenced by the effectiveness of intradermal vaccinations (BCG, smallpox, etc.). Its contact with the environment makes it a field of commensalism and bacterial and parasitic symbiosis that gives rise to stimuli that generate natural defensive mechanisms, while at the same time becoming, for this reason, the site of invasion of serious diseases that Like syphilis, leprosy, tuberculosis and fungal infections, they have, like the first two (and can have it, like the rest), their first appearance on the skin. Through the dermal vascular network, it acts as an effective temperature regulation mechanism; It has functions as an excrement by facilitating the excretion of large amounts of water, chlorides and some metabolites; and it also participates in the metabolism of vitamin D. The skin can: be considered as a mirror of what happens in the body, since it exposes its gigantic vascular network to view, which makes it accessible to very useful research; reflects the immunoallergic reactions of the organism, through its vascular and epidermal shock organs, and is capable of expressing the emotional state of the individual through vasomotor and secretory, sebaceous and sweat modifications, becoming a true "business card" for the relationship life of the individual. These functions facilitate the diagnosis of visceral clinical conditions, and are part of syndromes that present with ostensible dermatological manifestations. For example, pruritus with jaundice, in cases of chronic biliary obstruction

Dermatologic Patient Exam

The examination of the dermatological patient must conform to the fundamental principles required by the medical clinic. There are some differences in the dynamics, derived from the type of organ, one of them very important: the visual examination. The vast majority of dermatological problems are visible.

Hence, schematically, it is necessary to highlight that: a) the skin has its own pathology; b) the skin has a "borrowed" pathology, an expression of a general, organic process that is often reflected in it as the only (visible) clinical manifestation: metastatic tumor, lymphoma, etc .; e) the skin has a combined pathology; on the one hand it is manifested by alterations that are its own, and on the other by pathologies that simultaneously affect other sectors of the body: systemic lupus erythematosus, paraneoplasias.

History and physical examination

Usually the clinical history and the examination of the patient will allow us to discern if the responsibility for the management of the patient will be in charge of the dermatologist, the clinician or another specialist, or if it should be shared. Sometimes the skin condition appears so clear and simple that collecting more data may seem unnecessary.

But this same picture, when it becomes recurrent, will force the resources aimed at showing the causes that generate it to be deepened (retroauricular impetigo that precedes psoriasis, recurrent urticaria as a manifestation of an allergy to drugs or, more importantly, related to a connective tissue disease or as an expression of paraneoplasia).

The anamnesis should be aimed at collecting information on the patient's age, occupation, entertainment, time of evolution of the dermatosis, whether it is recurrent or not, mode of onset of the same, constitutional and subjective symptoms such as pain, paresthesia, disorders of the sensitivity, existence or not of itching; if it exists, find out its rhythm and intensity, probable seasonal or family nature, or, in its predecessors, data about other similar dermatoses, drug allergies and treatments carried out, be these indicated by the doctor, by other unauthorized persons or self-medication. Current or past general illnesses, focal infections, surgical interventions performed, etc will be investigated; The existence of atopic terrain, diabetes, venereal disease, tuberculosis and psoriasis in particular. The questioning can be concluded by asking if he is taking any medication.

This question is pertinent here, because, frequently, the patient forgets to refer to the existence of some general process, which may help to clarify the problem under consideration (digestive, mental, existence of heart disease and ingestion of drugs linked to them).

Regarding the physical examination, it is a fundamental principle of dermatology that the patient be examined naked. The ideal, which is not always specifiable, should be to examine the entire skin surface, including mucous and semi-mucous membranes. This can also be achieved with partial undresses. It follows from the foregoing the need for an adequate temperature, if possible not less than 18º since a lower temperature can modify the color of the skin, regardless of the discomfort it may cause to the patient. It is interesting to record here two phenomena that can occur at the moment in which the patient undresses. One of them is the appearance of an erythema of variable intensity, of irregular arrangement, which is located in the upper part of the thorax and on the skin of the neck, the erythema couldre;

The dermatologist must have instruments as modest as they are useful. Given the aforementioned importance of visual examination, a good source of light is necessary. The use of a magnifying glass at four or six times should be considered routine for a convenient magnification of the lesions. A watch glass, which can be replaced with a slide, is necessary to carry out the vitro pressure or diascopy, a maneuver that will allow us to differentiate a purple lesion from another that is not. A common needle and two test tubes for hot and cold water are essential to detect alterations in thermo-analgesic sensitivity, whereas tactile sensitivity can be discerned with a cotton swab.

The curette is necessary for scabbing off lesions that would otherwise be difficult to interpret; But the use of the curette is especially useful for the study of a psoriatic lesion through ~ "methodical scraping" of the same, which will show a special type of "candle candle" peeling that is proper to it. appearance of hemorrhagic spots, due to decapitation ~ the apex of the papillae that are hypertrophied. Finally, Wood's lamp, consisting of a high pressure mercury lamp, whose ultraviolet rays are filtered by a glass of silica and nickel oxide, constitutes a necessary resource to evaluate pigmentation alterations, show sources of mycosis, ringworm scalp,

Types of injury. Grouping or arrangement

The study of the skin requires prior knowledge of a series of signs that become essential to be able to interpret its pathology. Skin conditions manifest themselves through the so-called elemental lesions. There are criteria regarding their grouping, interpretation and individualization. From the didactic point of view, they can be classified into primitive and secondary.

• Primitives
  • Spot or macula
  • Papule
  • Tuber
  • Nodule
  • Blister
  • Vesicle
  • Pústula
• Scales
  • high schools
  • Scales
  • Loss of substance
  • Atrophy
  • Sclerosis
  • Scar
  • Scabs
  • Lichenification

This enumeration does not limit the existence of other elementary lesions, which can be simple, such as those mentioned, or composed by the confluence of them. Elemental erythematous-squamous lesion: psoriasis, cockade or cockade eczematis. Erythema, papule and bulla: polymorphic erythema and vesicle-associated erythema.

Spot or macula . It is a localized change in skin color, without alteration of the surface.

Erythema is, due to its frequency, the first order vascular stain. These erythemas can be congenital (flat angiomas of the face) or acquired (passive by circulatory stasis), but they are usually active, with an inflammatory cause. Its importance is variable, since both can constitute the only dermatological manifestation (for example, in erysipelas), and - what happens more frequently - constitute the natural satellite of numerous dermatoses. Due to their evolution, they can be acute or chronic.

According to their extension, they are grouped into circumscribed ones, such as in contact dermatitis that sometimes is manifested by that single symptom, or disseminated, and in this case they can reach variable configuration and extension (syphilitic roseola, which is observed especially in flanks , although it can be more generalized; uncharacteristic leprosy, where they can be manifested by one, several or numerous disseminated erythematous spots, which do not respect any skin sector, except the mucosa), or be more or less widespread as occurs when they are caused by solar rays, where they affect all areas exposed to said radiation.

A special reference requires the chapter on purples, which are cutaneous or mucosal capital hemorrhages, usually without an inflammatory component. Clinically they are represented by macular lesions that do not disappear with vitro pressure. 

They can reach any size. When they are small, pinpoint lesions, they are called petechiae; if they are larger, around 4 or 5 cm, they are called ecchymoses; while the name of vipers designates those elongated, in striae.

In general, their prognosis in dermatology, where they constitute true entities, is usually absolutely benign, as occurs with Schamberg's disease (vasculitis due to an exaggerated dose of vitamin B 12), Majocchi's telangiectatic purpura annular and, especially, senile Bateman's purpura. that selectively affects the back of the hands and forearms of subjects, especially women, who are around the fifth decade of life. But the prognosis is different when it comes to allergic purples or secondary to systemic symptoms (quinidine, leukemias, lymphomas, etc.).

Congestive lesions that are located on the face of young women, on the back of the nose and cheeks, where they adopt a distribution in butterfly wings, with coinciding purple lesions on the fingertips and earlobes, accompanied of constitutional symptoms, especially joint pain, have a very serious meaning and prognosis since this set of manifestations should suggest the diagnosis of lupus erythematosus.

It sometimes occurs that, in variable numbers, congestive spots covered with secondary scales, parenchymatous (that is, that retain their nucleus) appear, with selective localization on the elbows, knees and scalp especially. Faced with these manifestations, the diagnosis of psoriasis is imposed, of great practical importance because it is a genetic condition, due to its frequency (3% among the dermatological population) and due to the serious disorders that it can cause, because when generalizing or giving place to the appearance of joint pictures can invalidate the patient.

But when it comes to congestive spots, special emphasis should be placed on those caused by syphilis and leprosy. The dermatological hierarchy of these two diseases, since their evolution is always preceded by cutaneous manifestations, goes hand in hand with the simplicity of their diagnosis: it is only necessary to think about their existence, something that the clinician should never forget since all genital lesions especially it should be considered as syphilitic until proven otherwise; And the same happens with leprosy: in the presence of a congestive spot, of subacute or chronic evolution, whatever the patient's social background, the first thing that must be ruled out is this diagnosis, a very simple task due to the presence of sensitivity alterations thermoalgesic and tactile that characterize it.

Melanin-related pigmentation disorders are generically called dyschromias. and they can be due to an excess or deficit of it. Deficit dyschromias can be congenital and generalized, as in albinism, a genetic condition where there is a total lack of pigment and which can be accompanied by other abnormalities; for example nystagmus. Achromic nevus is characterized by a circumscribed lack of pigment. In turn, hypomelanotic spots can make up the Bourneville tuberous sclerosis picture. Among the acquired dyschromias the most important are, without. doubt, the achromic stain that characterizes incaractetic leprosy and vitiligo, both for its aesthetic importance and for its great tendency to become general

Melanic spots due to excess pigment can also be congenital or acquired. Among the first we have the Mongolian spot. The common pigmentary neva are not strictly congenital; but they are, however, the pigmented, hairy, giant intradermal nevi, which take up extensive sectors of the integument and which usually have a special distribution (nevus in "bathing suit"), a name that defines their location. This type of nevi has a severe prognosis since, in 20% of the cases, they would evolve towards malignant melanoma. Neurofibromatosis or von Recklinghausen's disease, the reverse of what is seen in tuberous sclerosis, is accompanied by pigmented spots (café au lait). Acquired pigmentations are usually circumscribed as occurs in chloasma, common in women, generally consecutive to pregnancy or ingestion of anovulatory drugs. In Addison's disease, diffuse pigmentations appear, more accentuated in exposed areas or subject to friction, especially localized in places of pressure, but also covering the oral and vaginal mucosa. The most frequent forms of diffuse skin pigmentation are those induced by the ultraviolet rays of the solar spectrum, which are located in all exposed areas. Another type of pigmentation is that which derives from contact with certain plants, rue, for example, and which follows subsequent exposure to the sun. X-rays can also cause pigmentation of varying degrees. Others are artificially acquired, such as tattoos, which can be voluntary or accidental. In Addison's disease, diffuse pigmentations appear, more accentuated in exposed areas or subject to friction, especially localized in places of pressure, but also covering the oral and vaginal mucosa. The most frequent forms of diffuse skin pigmentation are those induced by the ultraviolet rays of the solar spectrum, which are located in all exposed areas. Another type of pigmentation is that which derives from contact with certain plants, rue, for example, and which follows subsequent exposure to the sun. X-rays can also cause pigmentation of varying degrees. Others are artificially acquired, such as tattoos, which can be voluntary or accidental. In Addison's disease, diffuse pigmentations appear, more accentuated in exposed areas or subject to friction, especially localized in places of pressure, but also covering the oral and vaginal mucosa. The most frequent forms of diffuse skin pigmentation are those induced by the ultraviolet rays of the solar spectrum, which are located in all exposed areas. Another type of pigmentation is that which derives from contact with certain plants, rue, for example, and which follows subsequent exposure to the sun. X-rays can also cause pigmentation of varying degrees. Others are artificially acquired, such as tattoos, which can be voluntary or accidental. especially located in places of pressure, but also covering the oral and vaginal mucosa. The most frequent forms of diffuse skin pigmentation are those induced by the ultraviolet rays of the solar spectrum, which are located in all exposed areas. Another type of pigmentation is that which derives from contact with certain plants, rue, for example, and which follows subsequent exposure to the sun. X-rays can also cause pigmentation of varying degrees. Others are artificially acquired, such as tattoos, which can be voluntary or accidental. especially located in places of pressure, but also covering the oral and vaginal mucosa. The most frequent forms of diffuse skin pigmentation are those induced by the ultraviolet rays of the solar spectrum, which are located in all exposed areas. Another type of pigmentation is that which derives from contact with certain plants, rue, for example, and which follows subsequent exposure to the sun. X-rays can also cause pigmentation of varying degrees. Others are artificially acquired, such as tattoos, which can be voluntary or accidental. Another type of pigmentation is that which derives from contact with certain plants, rue, for example, and which follows subsequent exposure to the sun. X-rays can also cause pigmentation of varying degrees. Others are artificially acquired, such as tattoos, which can be voluntary or accidental. Another type of pigmentation is that which derives from contact with certain plants, rue, for example, and which follows subsequent exposure to the sun. X-rays can also cause pigmentation of varying degrees. Others are artificially acquired, such as tattoos, which can be voluntary or accidental.

Papules. They are circumscribed elevations of the skin, which do not contain fluid inside and resolve spontaneously, that is, they evolve to heal without leaving a scar. According to their location in the layers of the skin, they are classified as: a) epidermal, such as juvenile flat warts; b) dermal, comprising two types: edematous that are formed by collection of plasma in the dermis and whose classic type corresponds to the papule or welt of urticaria, and infiltrates such as the papule of the secondary period of syphilis; and finally e) the mixed, epidermodermic (or dermoepidermal) like those of the flat red lichen and those of the prurigos that, sometimes, are associated with a vesicle (papulovesicle). It should be noted that the infiltrated papules of syphilis, with selective localization on palms and soles,

Tuber . It is a solid, circumscribed, rounded formation, of slow evolution, elevated or not, of variable size, that originates in the dermis and that is not spontaneously resolutive, since always, whatever its evolutionary mechanism, reabsorption or ulceration, it will leave scar. As we can see, it presents opposite characteristics to the papule, but it far exceeds it in its pathological significance.

In fact, before the slightest doubt as to its interpretation, the step that is imposed is that of its histopathological study. The boil is its most typical and common expression, but not the most important. In the presence of a tuber, and this bases its clinical importance, the diagnoses that are imposed are particularly those that correspond to the large specific inflammations: syphilis. tuberculosis. leprosy and mycosis.

Nodules . Also called knots or knots, they are circumscribed indurations of the hypodermis. As a consequence of the intimate relationship that exists between the dermis and the hypodermis, many of these formations are hypodermothermic and eventually their pathophysiology is confused with that of the tubers. But some nuances related to their etiology, evolution and morphology make it advantageous to consider them as elementary lesions with their own characteristics. Nodules may become conspicuous on the skin surface, which may or may not be involved, or may only be perceptible on palpation. According to their evolution, they are classified as acute, subacute and chronic, a differentiation that has great diagnostic value.

A classic example of the acute form is erythema nodosum, a syndromic condition whose appearance in a child leads to the diagnosis of primary tuberculosis infection. It is of equal diagnostic importance in adults, since its presence makes it necessary to rule out the existence of reactive lepromatous leprosy.

Subacute nodules are divided into rubbery and non-rubbery. The gummy ones are characterized by their tendency to soften, ulcerate and drain to the outside and then heal after a variable period, which ranges between two and three months, leaving a pronounced scar.

With regard to its etiology, the same concepts that define the tubercle fit. Leprous gums are always related to a nerve, especially the ulnar nerve, and are almost exclusive to the tuberculoid forms, that is, to those associated with good immunological mechanisms. Among the non-gummy we must mention again leprosy in reaction. When this evolves subacute or chronic, it usually causes a special form of hypodermitis caused by the confluence of these nodules, which constitute a selectively localized plaque on the legs. It should be clarified that the evolution of the individual nodules is acute, but that the plaque becomes subacute or chronic due to permanent recurrences.

Tuberculosis is also represented in this group through an eruption of nodules of the same type, with selective localization in that sector, but which on palpation show a decrease in temperature compared to that of healthy skin.

This is the entity called Bazin's indurated erythema.

With regard to chronic nodules, practically the same defining considerations apply to subacute ones. But it cannot be less than emphasized that the interpretation of the rich pathology of the subcutaneous cellular tissue, constituting chronic panniculitis especially, is so complex that it will often be difficult to make a clinical diagnosis. On the other hand, its possible neo-formative etiology requires a meticulous study of the patient, where the histopathological examination occupies one of the first places.

Blisters and vesicles. They will be considered together, since their differences are more apparent than real. Both are circumscribed elevations of the epidermis that contain fluid. But although the vesicles are smaller than the bullae, since their size ranges between that of a pinhead and a small lentil, they are unilocular and are always located in the epidermis (a location that, as will be seen, can be shared with blisters), their formation mechanism is practically similar. However, from a clinical point of view it is advantageous to keep these names given that, in the face of a process characterized by the existence of vesicles, accompanied or not by erythema, the most frequent diagnostic possibilities that arise are: a picture of allergic origin such as eczema, dyshidrosis, or pictures of viral origin, but with a different nosological location. They are: herpes vulgaris and herpes zoster and chickenpox, also caused by the virus that produces zoster.

As regards the blisters, it should be noted that they represent the elemental lesion of pemphigus, a condition with a serious prognosis, fatal before the era of corticosteroids; it also integrates together with the vesicles especially, and with other lesions such as urticarial papules, the set of lesions that characterize Duhring's dermatitis. Paraneoplastic entity that is accompanied by an enteropathy similar to that of celiac disease in adults, characterized by an intolerance to gluten. Recent research links it to a functional deficiency of the spleen (hypo or anesplenia syndrome).

Pustules . They are elevations of the skin that contain pus. They can be epidermal, dermal, or follicular. The latter are the most representative, since they give rise to a series of malformative clinical pictures (hairy keratosis), due to avitaminosis and infections.

Among the latter, polymorphic juvenile acne will be retained, due to its frequency and practical importance.

The blisters and vesicles can become pustular due to bacterial contamination, constituting the vesiculopustules and the blisters purulent.

Scales . They can be primitive or secondary.

The primitives are the consequence of a normal process of the epidermis that constitutes the physiological desquamation or falling of scales, determined by the completion of the cycle of the cells that compose it. This phenomenon is easily visible in the newborn, in which it begins between the third and fifth day after birth. The phenomenon continues throughout life with permanent exfoliation of the horny layer, which allows the thickness of the epidermis to remain uniform; otherwise its retention would increase the thickness of the epidermis to constitute a keratosis or a hyperkeratosis, depending on its magnitude. Scales are seen especially in ichthyosis, ichthyosiform erythroderma, and keratoderma.

The scales, as secondary lesions, respond to a cellular alteration called parakeratosis; It is caused by the acceleration (of the growth rate) of the cell cycle, which gives rise to the appearance of nucleated horny cells, with a higher fat content than normal cells.

Parakeratosis is a common component of the histological picture of psoriasis.

Loss of substance . They result from tissue destruction. They are the consequence of the fusion of a previous lesion (specific infections, tumors, ruptured vesicles, blisters or pustules) although they can settle on apparently healthy skin. They can also be caused by mechanical factors (loss of substance due to repeated or repeated trauma such as scratching), physical (radiation, burns), chemical (usually professionals due to the handling of caustic products), and microbial and parasitic factors (specific infections: streptococcus, staphylococcus , mycosis), the latter constituting the most important group due to its pathological significance.

The semiological characteristics of the substance losses must be recorded in the anamnesis; the mode of onset, the treatments carried out, the evolution, which allows them to be grouped into acute, subacute and chronic; in the latter case they are called ulcers. It is important to study its location, cutaneous or mucosa, the state of neighboring tissues; its depth, since if they injure the basal layer it is an ulceration that will evolve leaving a scar, while if they do not they are designated as erosions or exulcerations.

Traumatic erosions, usually caused by scratching, are called abrasions. Cracks or fissures must be included here, which are solutions of continuity without loss of substance that are produced by a previous modification of the tissues, which prevents their free movement. The state of the edges, if they are cut to a peak, submined, and their coloring; the contours of the neighboring skin; the background of the injury, whether or not it shows a tendency to repair; if it is secreting, the type of discharge should be recorded: purulent, serous, etc .; finally, the existence or not of lymph node repercussions and their distribution (localized, disseminated, single or multiple) should be highlighted. '

A very important group of subacute ulcerations have been referred to when describing the gummy nodules. Two of them make up the group of venereal diseases, the soft chancre and the syphilitic.

The soft chancre, usually of genital location, is of acute evolution and has an incubation period of three to five days. It is a rounded ulceration, of variable size, up to one centimeter; their edges are cut to a peak and can be somewhat peeled; the background is yellowish and shows an abundant discharge, frankly purulent; the base is soft and painful; satellite lymph nodes are swollen and painful and progress to suppuration (chancre bubo). The causative agent is Ducrey's streptobacillus and it is investigated directly in the exudate.

Syphilitic chancre is of subacute evolution and can be genital or extragenital in location. It has an incubation period of around three weeks; It is constituted by a rounded erosion without edges (that is, without projection or elevation, since its limit is level with the bottom), of a red color comparable to that of muscular meat and, importantly, it has an indurated base; this is verified by taking the lesion between the thumb and index finger.

The induration may be of variable consistency, corrugated or parchment; it is accompanied by satellite lymphadenopathy made up of multiple, aflegmasic ganglia, one of which stands out due to its larger size. The nodes are located in the drainage territory of the corresponding lymphatics. The diagnosis is based on the finding of pale treponema, an investigation that is done by dark field.

It is necessary to emphasize that the description that precedes does not go beyond that of a typical chancre, since it can adopt very different characteristics, become ulcer, for example, variations that can make diagnosis difficult. The lesions of the secondary period are also usually erosions with localization in the buccal mucosa, the tongue and the palate especially, and genitals and perianals. Sometimes they can become ulcerative, as in malignant syphilis, where all the lesions can be of this type.

Among the chronic ulcerations, only those located in the lower limbs will be indicated.

Although in these sectors losses of substances of varied origin can be observed, such as those caused by specific inflammations, special reference deserves those of vascular origin, be they venous or arterial.

The former are typical of patients suffering from peripheral venous insufficiency, and are generically called leg ulcers, simple or varicose ulcers. The loss of substance observed in these cases has variable aspects and size, in relation to the terrain and the secondary infection that makes it chronic. The origin is usually traumatic and its location in the lower third of the legs is apparently linked to an incompetent perforating vein. Its main characteristics depend on the tissue damage caused by venous insufficiency and are manifested, according to its chronicity, by a series of symptoms that begin with edema of the leg.

In the state period, the main diagnostic character is given by the contours of the ulcer; edema is associated with a series of trophic lesions such as loss of skin annexes, dryness, pigmentation of hematic origin, and fibrosis of variable intensity; This condition is frequently complicated by the presence of eczema of bacterial origin. Importantly, resting with the raised limb benefits these patients considerably.

With regard to arterial ulcers, ischemic hypertensive ulcer, or Martorell's ulcer, where a decrease in the temperature of the affected limb is especially observed, without special concomitant injuries. The relevant symptom is constituted by the intense pain reported by the patient. Contrary to what occurs in venous ulcers, bed rest, with elevation of the affected limb, intensifies the pain.

Lastly, plantar perforator disease or plantar ulcer will be described, although it may eventually have other locations. It is usually located in the skin that corresponds to the head of the first metatarsal or in any other neighboring sector subjected to pressure. The morphological aspect of this lesion, which can begin as a painful callus, is reduced to the presence of an intense hyperkeratosis, which is the site of an ulceration, sometimes deep enough to affect (or complicate) the tendons, the joints and neighboring bones. The injury may be painful spontaneously or under pressure, but is usually anesthetic. Its etiology is linked to important traffic disorders. Its presence makes it necessary to rule out leprosy, nervous syphilis, taboos in particular, diabetes or syringomyelia.

Losses of substance can also be observed in the mucous membranes. As its frequency is higher in the oral mucosa, the description will be limited to this sector of the body. Of course, any of the ulcer processes mentioned can be located in the oral mucosa. Others, also observable on the skin, vesicles and blisters, break easily and are replaced by a loss of substance. Finally, other lesions that do not exist in the skin can be found here, observing a particular morphology and evolution in the oral mucosa, as well as their complications. Such is the case of acute ulcerations called canker sores.

These are lesions of possibly viral etiology, of painful, acute evolution and spontaneous healing. Thus considered they can be defined as an intrascedent episode. But in some subjects, the lesions recur and the subjective symptoms are so intense that they can make the patient's relationship life difficult. On the other hand, and of greater prognostic importance, is its appearance in the genitals and eyes, being associated with very serious lesions in the latter (Beh9et syndrome, bi / tripolar). Recurrent necrotic periadenitis, characterized by chronic recurrent ulcerations, which especially affect the tongue, are considered a chronic type of canker sores.

Atrophy, sclerosis and scar . They will be considered as a whole given that, despite having a meaning. different, they can adopt a very similar morphological appearance and also, on occasions, they are associated.

Atrophy is a decrease in the number and volume of the constituent elements of the skin or some of them, in particular elastic tissue. The process involves both the dermis and the epidermis, consequently including smooth muscle fibers and appendages; If the tissue damage reaches the subcutaneous cell it is called panatrophy. The color and consistency of the skin are diminished. Atrophies can be congenital and such is the case of atrophic nevus, a rare, circumscribed malformation made up of atrophic areas, sometimes lined with telangiectasias (small dilated vessels).

The acquired forms are numerous and can give rise to very complex clinical pictures that are sometimes associated with cutaneous sclerosis. One of them is sclerosing panatrophy. Facial hemiatrophy overflows its name since, in addition to being a progressive condition with muscular and bone alterations, it can be accompanied by skin sclerosis and eye and nervous system disorders. Atrophy, as a sequel to well-defined skin entities, is equivalent to a scar. Sclerosis or dermatosclerosis is constituted by a condensation of the components of the skin, the dermis in particular, increased or not in number and volume, which slide less easily between each other. 

Sclerosing skin may appear thickened, apparently normal, or thinned, simulating atrophy. Its consistency is always increased, it is difficult to depress or fold, and it can adhere to deep planes. Dermatosclerosis may present in multiple plaques, or plaque scleroderma, or generalize as occurs in progressive systemic sclerosis. There are other acquired processes that associate sclerosis with atrophy, such as radiodermatitis and dermatosclerosis of the varicose legs. The scar, on the other hand, constitutes a replacement tissue, a consequence of the repair of a previous process that has destroyed the basal layer. A destruction of the apricots of variable magnitude is added here. Thus defined, scars can be classified as aesthetically acceptable, When its characteristics do not substantially modify the appearance or function of the skin, or vicious, otherwise. Sometimes they lead to the formation of an infiltrated fibrous elevation, which may be accompanied by subjective symptoms; this type of scar is called a keloid, and due to its histological characteristics - intense fibrosis seeded by mast cells - it can be considered a benign tumor.

The scar may be associated with frankly evolutionary processes, as occurs with a variety of basal cell epithelioma called the cicatriza plane /; This epithelioma is made up of a plaque that progresses along its edges but leaves a dull white scar in its center, the result of limited local healing, but which can lead to recurrences.

Scabs . They result from the desiccation of secretions.

It is reasonable to assume that they will always be covering a loss of substance, erosions, ulcerations, most often associated with ruptured vesicles, blisters or pustules. According to the type of secretion that originates them, they can be hematic, serous, purulent or combined, serohematic, combined with each other. Meliceric scabs are very typical and frequent, so called because of their resemblance to honey, which follow the rupture of the impetigo blisters. As it is an expired lesion, its removal is essential to clearly objectify the character of the underlying lesion. No crusting is observed in humid areas such as mucous membranes or folds.

Lichenification. It consists of a set of morphological alterations closely associated with pruritus. These begin clinically with a mild inflammatory process accompanied by itching, the intensity of which is not related to skin lesions. In its period of state, an increase in the thickness of the skin is observed, which is associated with an accentuation of its folds, with slight desquamation and pigmentation. The crisscrossing of the folds involves papuloid elevations between their meshes that give it an appearance similar to lichen planus, from which it derives its name. It is important to note that scratching trauma, induced by pruritus, causes this type of injury only in predisposed subjects; In other words, its production requires the prior existence of a terrain that enables this response. Lichenification can be primitive, settling on apparently healthy skin; in these cases it is circumscribed and gives rise to the picture known as lichen simple de Vida. Secondary lichenification is usually diffuse and complicates pre-existing pruritic dermatoses that usually present with multiple lesions such as psoriasis and atopic eczema in particular. This type of eczema, genetically determined and associated with asthma and rhinitis, is characterized immunologically by the existence of an antibody, reagin, identified with immunoglobulin E, which is increased. Clinically, its usual location, which is in the folds, especially the elbow and popliteal hollows, facilitates diagnosis. Secondary lichenification is usually diffuse and complicates pre-existing pruritic dermatoses that usually present with multiple lesions such as psoriasis and atopic eczema in particular. This type of eczema, genetically determined and associated with asthma and rhinitis, is characterized immunologically by the existence of an antibody, reagin, identified with immunoglobulin E, which is increased. Clinically, its usual location, which is in the folds, especially the elbow and popliteal hollows, facilitates diagnosis. Secondary lichenification is usually diffuse and complicates pre-existing pruritic dermatoses that usually present with multiple lesions such as psoriasis and atopic eczema in particular. This type of eczema, genetically determined and associated with asthma and rhinitis, is characterized immunologically by the existence of an antibody, reagin, identified with immunoglobulin E, which is increased. Clinically, its usual location, which is in the folds, especially the elbow and popliteal hollows, facilitates diagnosis. it is characterized immunologically by the existence of an antibody, reagins, identified with immunoglobulin E, which is increased. Clinically, its usual location, which is in the folds, especially the elbow and popliteal hollows, facilitates diagnosis. it is characterized immunologically by the existence of an antibody, reagins, identified with immunoglobulin E, which is increased. Clinically, its usual location, which is in the folds, especially the elbow and popliteal hollows, facilitates diagnosis.

Pathophysiology of elemental lesions

Dermatoses recognize multiple etiopathogenic causes: malformative, inflammatory, degenerative, bioplastic and neoplastic. Its origin can also be traumatic, physical or chemical, either accidental or self-caused. Objective or subjective skin manifestations, such as pruritus, for example, can often be determined or influenced by emotional causes. By the way, the influence of the psyche on the skin is beyond doubt, a factor that should always be borne in mind, since, to a greater or lesser degree, it contributes to modifying the evolution of dermatoses.

There are pictures authentically linked to psychic factors such as neurotic excoriations or Munchausen syndrome; In the first case, the patient accepts its clinically suggested, self-caused origin, since erosive or ulcerated lesions usually have a linear arrangement and are located in skin sectors that are within reach of the patient's nails; in the second, characterized by the most confusing and inexplicable manifestations (usually severe, such as loss of substance from any location), the patient, on the contrary, not only hides his origin but also apparently complies with all the indications that the patient Your doctor suggests, even if they are aggressive (such as a biopsy, for example), in an attempt to continue to hide the cause of your injuries.

Among the other causes cited, inflammation, acute or chronic, prevails, both due to its frequency and the severity of the conditions it can give rise to.

Acute inflammations. They are represented basically by the tetrad of Celsus, subject to variations subordinate to the organ. The classic example in dermatology is the staphylococcal abscess. But the usual thing is that the pain is replaced by itching and that the tumor is not easily noticeable (generalized edema). The phlogistic stimulus initiates the condition causing an acute paroxysmal capillary vasoconstriction followed by vasodilation, which produces congestion that is clinically translated into erythema. If vasodilation is maintained, serous (or plasma) exudation occurs, which can accumulate in the papillary dermis with consequent edema; if it is circumscribed, it gives rise to the urticaria papule or welt; but if it invades the hypodermis, it causes a tumor lesion that is clinically expressed by angioneurotic edema or giant Quincke's edema. Exudation can reach the epidermis; in this case the morphological responses will be varied; If it infiltrates the mucous body, it will cause the lysis of some cells, giving rise to a microscopic cavity, the primordial vesicle. The progression of this edema, invading the mucous body, causes what is called spongiosis, given the resemblance it gives, histologically, to a sponge; This phenomenon is clinically evidenced by the appearance of vesicles, which, together with the erythema and secretion to which their rupture gives rise, with the consequent formation of scabs, constitute the elemental lesion of eczema. But if the serous invasion remains in quantity and with sufficient intensity will cause the formation of the blister; taking into account the cleavage planes of the epidermis, these will be divided into superficial, subcorneal,

The group of lesions mentioned synthesizes the clinical picture and pathophysiology of Duhring's dermatitis. On the other hand, bacterial contamination of the blisters and vesicles leads to pustular lesions, vesiculopustules, or purulent blisters. The true pustules are located in the hair follicle and are due, in general, to the primitive bacterial or fungal aggression of the pilosebaceous follicle, causing acute folliculitis that can become chronic due to their persistence, since they are due to the repeated recurrence of the infection . The lesions described, of liquid content, when broken by the action of scratching, rubbing, or spontaneously, give rise to superficial losses of substance, erosions or exulcerations, since the deep ones originate from the fusion of tubercles or of a rubber,

Subacute inflammation . When the patient suffers from a pruritic dermatosis, which evolves with certain chronicity, usually with multiple clinical manifestations, the trauma caused by scratching causes a hyperplasia of the mucosal body, which increases in thickness; This alteration is called acanthosis. At the same time, nonspecific cellular infiltrates develop in the dermis. The morphological (or clinical) picture of lichenification then appears, which in this case is secondary and complicates the pre-existing picture.

This type of lesion is usually accompanied by a certain degree of pigmentation due to the proliferation of melanocytes that accompanies the hyperplasia of keratinocytes. Other times these modifications can appear on apparently healthy skin, as a consequence of repeated scratching induced by primitive itching. If the lesions are diffuse they produce diffuse primitive lichenification; but if they are localized, circumscribed, usually multiple, they give rise to the formation of prurigo papules. The association of acanthosis and papillomatosis originates a lesion called vegetation. This clinical type, considered by some to be just another elementary lesion, can be observed in secondary syphilis (hypertrophic perianal papules), also characterizing a clinical form of pemphigus, pemphigus vegetative.

The histological manifestations of recent syphilis (inoculation chancre, secondary lesions) are initially characterized by an infiltrate that is predominantly perivascular and that is made up of polymorphonuclear cells, to which lymphocytes and plasma cells selectively distributed around the vessels are added; In addition, these show variable degrees of endoarteritis and endophlebitis, with the presence of treponemes. Obliteration and thrombosis of some of these vessels causes foci of necrosis that give rise to the erosion that characterizes chancre and papuloerosive lesions. If the necrosis is more intense, the chancre may be ulcerative.

Chronic inflammations . The infiltrates, in this case, are constituted by the hyperplasia of the cells of the macrophage system, giving rise to the formation of granulomas, which express the epithelioid cellular response to the attack of microorganisms. They can be necrotizing, as in specific large inflammations, and non-necrotizing, as in sarcoidosis. It is especially interesting to consider tuberculoid granulomas whose presence characterizes large specific inflammations, in which they constitute the expression of a state of host resistance to the aggression of bacterial, parasitic and fungal agents.

Thus, in tuberculosis, where they are accompanied by caseosis, constituting Koster's follicle, they will evolve causing ulceration. A similar event occurs in tuberculoid leprosy, a clinical form with a good prognosis, mainly from the immunological point of view. In these cases, generally abaciliferous, the granulomas adopt a typical neural distribution, destroying the nerve fillets and, consequently, causing the sensitivity disorders that characterize them. They can affect nerve trunks such as the ulnar and the auricular branch of the superficial cervical plexus, more frequently, causing hypertrophy of these trunks and, eventually, the development of an abscess. This will lead to the formation of a localized ulceration in the path of the nerve and the appearance of trophic alterations such as muscle atrophies, claw hands, etc. Since the histiocytic granulomas constituted by Virchow cells, loaded with Hansen's bacilli, typical of the lepromatous form, have a significance opposite to the previous one. In these last two cases, the granulomas have as their starting point the chronic inflammatory infiltrate, lymphohistiocytic, distributed around the organized structures of the dermis, which characterize the erythematous, achromic or erythematous hypochromic lesions of the indeterminate form of leprosy; but here they adopt, again, the disposition that characterizes them and that gives them a high degree of specificity: the destruction of the nerve fillets. etc. Since the histiocytic granulomas constituted by Virchow cells, loaded with Hansen's bacilli, typical of the lepromatous form, have a significance opposite to the previous one. In these last two cases, the granulomas have as their starting point the chronic inflammatory infiltrate, lymphohistiocytic, distributed around the organized structures of the dermis, which characterize the erythematous, achromic or erythematous hypochromic lesions of the indeterminate form of leprosy; but here they adopt, again, the disposition that characterizes them and that gives them a high degree of specificity: the destruction of the nerve fillets. etc. Since the histiocytic granulomas constituted by Virchow cells, loaded with Hansen's bacilli, typical of the lepromatous form, have a significance opposite to the previous one. In these last two cases, the granulomas have as their starting point the chronic inflammatory infiltrate, lymphohistiocytic, distributed around the organized structures of the dermis, which characterize the erythematous, achromic or erythematous hypochromic lesions of the indeterminate form of leprosy; but here they adopt, again, the disposition that characterizes them and that gives them a high degree of specificity: the destruction of the nerve fillets. they have a meaning opposite to the previous one. In these last two cases, the granulomas have as their starting point the chronic inflammatory infiltrate, lymphohistiocytic, distributed around the organized structures of the dermis, which characterize the erythematous, achromic or erythematous hypochromic lesions of the indeterminate form of leprosy; but here they adopt, again, the disposition that characterizes them and that gives them a high degree of specificity: the destruction of the nerve fillets. they have a meaning opposite to the previous one. In these last two cases, the granulomas have as their starting point the chronic inflammatory infiltrate, lymphohistiocytic, distributed around the organized structures of the dermis, which characterize the erythematous, achromic or erythematous hypochromic lesions of the indeterminate form of leprosy; but here they adopt, again, the disposition that characterizes them and that gives them a high degree of specificity: the destruction of the nerve fillets.

All of the above allows us to deduce how the histological examination is capable of showing the relative unity of the inflammatory process in the genesis of dermatoses that have this origin.

But this description of the elemental lesions would be incomplete if reference were not made to the semiology of the skin adnexa.

Allusion has already been made to the pilosebaceous unit. In many dermatoses the follicle is involved in the morbid process, but without any special significance. Other times, on the contrary, the process is located in the follicle and gives rise to folliculosis, usually of infectious origin.

It is important to note that the pilosebaceous orifice, the acrotrich, constitutes, along with the acrosyringium, the most vulnerable point of the epidermal shell. These holes are normally populated by powdery foreign bodies and by various microbes, common hosts of the epidermis. It goes without saying that any circumstance that decreases the resistance of the organism, that exalts the virulence of these germs, or the association with other more virulent parasites, will cause a suppurative inflammatory process.

The follicle also shares other pathologies with the rest of the skin and the body. Follicular syphilids of the secondary period are very characteristic. In tuberculides, which appear in subjects who have a high degree of immunity to Koch's bacillus, but who only partially fulfill its postulates, the tuberculoid structure without histological caseosis is the usual one; In short, the presence of this histological infiltrate artificially enriched the spectrum of diseases of this origin.

The list of processes that affect the hair follicle is numerous; Consequently, those most frequently observed in practice will be highlighted: seborrhea, polymorphic juvenile acne, hypertrichosis, hirsutism and the so-called seborrheic alopecia. This designation does not correspond, because seborrhea defines an increase in sebaceous secretion, which exists as a pathology of the respective gland, but is not necessarily accompanied by alopecia, which can occur with normal secretion of the gland. Seborrhea is the basis of acne through the increase in free fatty acids. These manifestations are typical of adolescence; acne heralds puberty and alopecia can start at the age of fifteen. Hypertrichosis, on the other hand, it is represented by the excess of terminal hairs where usually only hairy hair is observed. On the other hand, hirsutism, typical of women, defines the appearance of terminal hairs in regions usually devoid of it or well populated only with hairy hair (beard, mustache, etc.).

Diagnosis

Dermatological semiology requires the use of an appropriate language for the correct description of the lesions shown by the patient. Its application will facilitate teaching and mutual understanding, since it will allow highlighting the importance of morphological details that characterize dermatoses, which can then be more easily identified.

The clinical examination requires, first of all, an evaluation of the patient's skin type since, even normally, characteristics can be observed that indicate a proclivity to certain dermatoses: oily skin that predisposes to acne or eczematids or that of those Caucasoids from northern Italy blond subjects with light skin and eyes highly susceptible to ultraviolet radiation, which creates in them a special predisposition to skin cancer in areas exposed to sunlight.

Once the skin type has been identified, the next step is to study the dermatosis that is the reason for the consultation. The group of lesions that compose it is called an eruption, and its histopathological formation involves cellular elements that normally cannot be found in the skin, at least in such abundant and coincident numbers. Inflammation prevails among the causal factors, which can often lead to extremely serious conditions. Nosologically, the morbid entity must be differentiated from the skin reaction. The first is manifested by heterogeneous lesions that respond to a single generally known etiology (syphilis, leprosy, tuberculosis, mycosis). The second, in. On the other hand, it is a syndrome that is expressed with the same type of injury, but that recognizes various causes (urticaria, eczema, drug allergy, erythema nodosum).

The examination must rule out the coexistence of constitutional symptoms or any other cause that affects or affects the general condition. Although it is convenient to start it by studying the dermatosis that the patient presents, in no way can it be limited to it. Thus, it is necessary to have an overview of the state of the skin in other sectors, to investigate the probable extension of the dermatosis to areas not perceptible or accessible to the patient, such as the scalp, the retroauricular regions, the back, the nails and accessible mucosa, the mouth in particular.

The study of the eruption should be aimed at identifying the other elemental lesions that compose it. The color, the size, the shape and the data provided by the palpation, such as its consistency, temperature, mobility and sensitivity are especially interesting.

It may be that the injury is single (solitary injury) or it may be made up of multiple elements.

In this case, the eruption may be formed by similar elements (monomorphic eruption) or by different types of lesions (polymorphic eruption). Often, monomorphic eruptions - pemphigus vulgaris among them - can present a pseudo polymorphism subordinate to the existence of young lesions, new initial lesions, or as a consequence of other lesions modified by pyogenic or traumatic complications such as scratching.

Another aspect to be determined is the way in which the lesions are grouped, which can be herpetiform, serpeginous, arcuate, and reunited or networked. According to the distribution of the lesions and their extension, the eruption can be defined as discrete, usually localized; disseminated when it affects several regions; generalized if it respects only some sectors to become universal, or erythrodermic when areas of healthy skin are practically not observed. It is important to note that erythroderma are inflammatory and congestive syndromes of various significance and importance. They can be grouped into different types.

Some are congenital and sometimes incompatible with life, such as ichthyosiform congenital erythroderma; they are frequently acquired and can be grouped into three types: a) vascular, which is equivalent to eczema; b) reticular, exclusive of lymphomas such as mycosis fungoides or Hodgkin, especially, and e) epithelial, among which psoriasis occupies a first place. This type of syndrome, initially included within the group of erythematous squamous conditions, is nothing more than a morphological type, since once its etiology is known, it is integrated into the group that corresponds to it.

The distributive pattern allows adding some important aspects such as symmetry, its location in exposed areas, folds, hairy areas, all factors that can modify the morphology of the dermatoses. The examination should be completed with a careful search for lymphadenopathy and a general clinical evaluation.

It should be borne in mind that in the skin examination the morphological diagnosis is only an initial step, very important, by the way, to arrive at the final diagnosis that constitutes the objective. Magnification with a magnifying glass, transillumination, compression with a slide to differentiate congestive from hemorrhagic lesions, and examination with Wood's lamp (long-wave ultraviolet light) contribute to the evaluation of the lesions.

Routine and specialized laboratory are important in the study of the patient with skin lesions; It includes the hemogram, erythrocyte sedimentation, uremia, glycemia, cholesterol, triglycerides, uricemia, calcium, phosphataemia, ionogram, proteinogram and enzymes, as well as the proteinogram, the investigation of LE cells, of the antinucleus factor (AN), of anti-DNA antibodies , latex and Rose-Ragan tests, dark chamber examination, VDRL, antistreptolysins, Widal, PPD, monotest, rubella antibodies, immunofluorescence and histological studies (biopsy).

BIBLIOGRAFIA
Braverman, I.: Skin Signs of Systemic Disease. W.B. Saunders Co., Philadelphia, 1981.
Fitzpatrick, T.B. and Bernhard, J.D.: The structure of skin lesions and fundame:iltals of diagnosis. In Fitzpatrick, T.B. et al. (eds.): General Medicine, 3rd. ed. Me Graw-Hill Book Co., New York, 1987.
Rook. A. and Wilkinson, D.S.: The principies of diagnosis. In Rook, A. et al. (eds.): Textbook of Dermatology. Blackwell Scientific Publications, Oxford, 1979, p. 37.