Skin Disorders Guide

The “attributes of lesions” represent the adjectives that are used to modify those nouns. In both verbal and written description it desirable first to pick an appropriate noun from the list of lesions and then to add as many modifiers as necessary to accurately complete the characterization of the lesion in question.

Margination

Margination is the shape of the lesion as it is seen in cross section. It describes the transition zone between normal and abnormal skin. Margination is generally stated to be sharp or diffuse.

A lesion is said to be sharply marginated when the cross-sectional shape of the lesion is square shouldered or dome shaped and the transition from normal to abnormal skin occurs abruptly (in the space of 1 mm or less). Note that to be classified as a sharply marginated lesion, sharpness of the border must be maintained around the entire circumference of the lesion.

On the other hand, a lesion is said to be diffusely (or poorly) marginated when the cross-sectional shape of the lesion is slope shouldered and the transition zone is less abrupt (greater than 1 mm). Note that a poorly marginated lesion may have, within the total circumference of the lesion, a few segments that are sharply marginated.

Margination is particularly important in distinguishing lesions of the papulosquamous group (group 9) from those of the eczematous group (group 10). Papulosquamous lesions are sharply marginated, whereas eczematous lesions are poorly marginated.

Configuration

Configuration is the shape of a lesion. Most lesions are circular. A few lesions are oval-notably those of pityriasis rosea and parapsoriasis, the rest are “irregular” in shape. Specific examples of lesions with an irregular shape include linear lesions, angular lesions, and those lesions variously and synonymously described as gyrate, polycyclic, or serpiginous. These latter lesions, possessing a scalloped type of border, generally arise when adjacent lesions centrifugally enlarge and merge into a single confluent lesion. Two special types of configuration should be noted. Nummular lesions are sharply marginated, round lesions that are coin sized (3 to 10 cm in diameter) and coin shaped. Annular lesions are round or scalloped lesions in which the center has cleared, leaving a thin, ring-like, active border.

Scale

Cutaneous epithelial cells become flattened envelopes packed with keratin as they move from the basal layer to the outer surface of the skin. In normal skin, these cells are shed imperceptibly on a continuous basis. In many types of abnormal skin, the equilibrium between production and loss is disturbed such that these dead keratinocytes build up on the skin surface as visible and palpable scale.

Three types of scale can be identified. The first is psoriatic-type scale that is characterized by easily palpable and visible white, silver, or gray flakes. The individual flakes are large enough to be picked up with a small forceps. The white color occurs because the flakes are loose and lifted such that there are two surfaces that refract light. This explanation is the same as that which accounts for the white color of the distal tip of the fingernail where it becomes detached from the underlying nail bed. The second is Pityriasis-type scale that, because of the small flake size, is hardly visible or palpable. It becomes readily apparent only when scraping with a fingernail or a blade reveals its fine, white, powdery character. The third is lichen-type scale that is characterized by slightly palpable roughness and a shiny, somewhat translucent appearance. Whiteness is usually not present because the scale is tightly attached to the underlying epithelium. The lichen-type scale, in contrast to the psoriatic-type scale, is analogous to the proximal, attached, and colorless portion of the nail plate.

Crust

The formation of crust occurs when plasma exudes through a damaged or absent epithelial surface. It consists of the plasma proteins that remain after the water component of plasma has evaporated. Crust feels rough on palpation and is visible as amorphous or granular material. The color of crust is highly variable. Normally, it is yellow or yellow-brown. If heme pigment is present, however, the crust becomes red, blue, or black. The thin layer of crust that covers a shallow erosion is loosely adherent, whereas the thicker, darker crust (known as eschar) present in some ulcers is tightly adherent because of the presence of fibrin. Scab is a colloquial term for crust.

Color

The color of lesions is dependent on several factors. Red hues are related to blood flow and/or the presence of inflammation. Brown, black, and blue hues are due to the presence of either of two pigments-melanin or heme. White hues are most often due to the absence of normally present melanin pigment. Yellow hues are due to the abnormal deposition of certain chemicals, lipids, or proteins.

The true color of a lesion may be difficult to recognize. First, any color contributed by scale should be disregarded. The actual color of a heavily scaled lesion can be determined by looking at the peripheral margin of the lesion or by scraping away a little scale. Second, color contributed by crust should also be disregarded. In fact, where crust covers an ulcer or erosion, it is not necessary or useful to determine the color of the base. Third, the term “skin-colored” applies to the color of the patient’s normal skin. Thus, a skin-colored lesion may appear brown in those who are heavily pigmented and white in those who are lightly pigmented. Fourth, red coloration may be undere stimated or even missed in individuals with deeply pigmented skin.

Consistency

Most lesions should be palpated to determine their consistency. Macules and patches will have no sense of substance. Soft papules, plaques, and nodules are compressible; firm lesions cannot be compressed at all. When cysts are compressed, there is initially a feel of “give,” but further compression reveals a sense of firmness. Most inflammatory (red) lesions will have a medium (or intermediate) consistency. It is not important to determine the consistency of vesicles and bullae.

Pruritus

Pruritus is the sensation of itching. The intensity of itching experienced by a patient depends on several factors. First some diseases are inherently more pruritic than others. Second, some individuals, especially those who are genetically atopic have a lower threshold for itching than do others. Third, lesions located in warm moist areas are more pruritic than similar lesions located elsewhere. This phenomenon may be related to a chemical effect. of retained sweat .Fourth, psychologic factors, specifically anxiety and depression, greatly intensify the perception of itching.

Response to the sensation of itching is quite variable. Some patients, particularly during the day when t.he mind is otherwise occupied, can ignore the sensation entirely. Most patients, however, respond with scratching or rubbing of the skin.

Scratching, when it is vigorous, results in linear or angular shallow erosions known as excoriations. The presence of excoriations is positive proof that. scratching has gone on regardless of the occasional patient’s statement to the contrary. However, it is possible for the patient to scratch without being aware of it. This occurs, in the day time, when scratching becomes a “reflex” habit and, at night, in the lighter stages of sleep. Patients who respond to pruritus with chronic rubbing rather than scratching develop lichenification. Lichenification is identified by a trio of easily recognized changes, palpable thickening of the skin, accentuated skin markings, and the presence of lichen-type scale. The development of lichenification is analogous to callus formation when the palms and soles are subjected to chronic trauma. Excoriations and lichenification are characteristic features of eczematous disease.