These are of manifold varieties, of which the most important
are scales, excoriations, fissures, crusts, ulcers, and scars.
Scales (Exfoliating Epidermis, Epidermal
Exfoliations, Squames, Squamae).
Scales are dry or greasy laminated masses of
epidermis. The body ordinarily is undergoing a scarcely perceptible
desquamation in the form of tiny thin epidermic particles. When the formation
of epidermal cells is rapid or the process of normal cornification is
interfered with, pathologic exfoliation occurs, producing scales. These vary in
size, some being fine, delicate, and branny as in pityriasis versicolor, others
being coarser as in eczema and ichthyosis, while still others are stratified as
in psoriasis. Large sheets of desquamated epidermis are seen in exfoliative
dermatitis and scarlet fever. Generally the exfoliations are thin, dry, brittle
shiny flakes, but sometimes they are greasy and dull from the sebum and sweat.
They vary in color from whitish, grayish to yellowish or brown from the admixture
of dirt; and occasionally they have a silvery sheen from the permeation of the
cells with air. Scales may be adherent ( as in lupus erythematosus) or loose.
Micaceous scales are characteristic of psoriasis.
Scaling is common in a large number of inflammatory diseases of the
skin, being associated with edema of the epidermis, and parakeratosis.
Excoriations (Abrasions, Erosions, Scratch
Marks).
An excoriation is
Excoriations may be accompanied by inoculation
of pyogenic micro-organisms and the formation of pustules, occasionally
associated with enlargement of the neighboring lymphatic glands.
Fissures (Cracks, Rents, Clefts, Rhagades).
A
fissure is a linear cleavage into the epidermis or the epidermis and the
corium, caused by disease or injury. These lesions may be single or multiple,
and vary from tiny cracks to clefts several millimeters in length, with sharply
defined margins. They may be dry or moist, reddish, straight, curved,
irregular, and branching. They occur most commonly when the skin is thickened
and inelastic from inflammation, especially in regions subjected to frequent
movement. Such areas are the flexures, the palms, the clefts between the
fingers and toes, and at the angles of the mouth, about the nares, auricles,
and anus. When the skin is dry and sensitive, exposure to cold and wind, or the
action of soap and water may produce a stinging, burning sensation and
fissures—"chapping." Pain often accompanies movement of the parts by
opening or deepening the cracks or forming new ones.
Crusts (Scabs, Crustae).
Crusts are dried masses of serum, pus, or blood, usually
mixed with epithelial and bacterial debris. They vary greatly in size,
thickness, shape, and color according to their origin, composition, and the
amount of discharge. They may be dry, soft, friable, and superficial, as in
impetigo contagiosa; yellowish, as in favus; thick, hard, and tough, as in
third degree burns; or lamellated, elevated, brownish, blackish or greenish
masses as in late syphilis. The latter have been described as oyster
shell-shaped crusts ( ostraceous ) and are known as rupia. When thin crusts
become detached, the base may be dry, or red and moist, and heal, leaving a
smooth normal skin surface. Lesions with thick crusts covering ulcers are
likely to leave scars.
Ulcers
(Ulcera).
These are rounded or irregularly shaped excavations due to loss of substance
from gradual necrosis. They vary in size from that of a split pea to several
inches in diameter. They may be shallow, involving only the epidermis, as in
cases of pemphigus, the base being formed by the papillary layer, or they may
extend deep into the corium or even reach into the subcutaneous structures, as
in rodent ulcer.
Scars
(Cicatrices).
Scars are new formations of connective tissue which replace loss
of substance in the corium or deeper parts as a result of injury or disease,
being part of the normal reparative and healing process. They are well supplied
with blood capillaries and nerves. Their size and shape are determined by the
form of the previous destruction. In certain dermatoses the process of
absorption of cellular infiltration leads to scar formation, as in lupus and
syphilis. In others, pressure leads to thin, atrophic scars or the fibrous
elements develop into neoplastic overgrowths, as in keloid. Cicatrices may be
smooth or rough, pliable or firm, and tend at first to be pink or violaceous,
later becoming white and glistening, and rarely pigmented.
Scars with certain characteristics are typical of individual
diseases of the skin so that they are of diagnostic value. Those of lupus erythematosus
are shiny, thin, rigid, telangiectatic and minutely pitted, corresponding to
glandular orifices; those from lupus vulgaris, tough and fibrous, occasionally
cordlike or with scaling at the edges; those which follow burns are a mixture
of thin, depressed, atrophic and hypertrophic, raised or fibrous lesions with
keloidal tendency; those of smallpox, innumerable small white rounded pitlike
depressions, usually on the face; those which follow the involution of
syphilids are thin, crinkled, and papery. Some individuals and some regions
such as the anterior chest are especially prone to scarring.
Scars are persistent but nevertheless are
inclined to become less noticeable in the course of time. On the other hand,
sometimes they grow thick, tough and corded, forming a hypertrophic scar.
Rarely the keloidal scar tissue may spread into the neighboring normal skin.
Histologically a useful diagnostic feature is
the absence of interpapillary pegs overlying the scar. After destruction of the
epidermis, the interpapillary pegs do not regenerate with the rest of the
epidermis. The connective tissue in the corium appears in broad bundles which
interlace and blend with the neighboring normal fibrous tissue. In young scars
the nuclei are larger and more closely placed whereas in old scars the nuclei
are sparse and small and the bundles are smooth and hyalinized.
Distribution and Arrangement of
Lesions
Lesions may be few or nu-merous, and they may be discrete, or
coalesce to form patches or peculiar configurations. They may appear over the
entire body, sometimes following the lines of cleavage, or they may follow the
course of nerve trunks, as in herpes zoster and leprosy, or they may form
groups, rings, crescents, or grotesque patterns. Further details concerning the
distribution and arrangement of lesions are given under Diagnosis.