SYMPTOMATOLOGY
The clinical pictures presented by the vast number of skin
diseases vary widely and yet in some instances possess identical features, thus
creating problems in diagnosis. The same disease may show variations under
different conditions and in different individuals. Symptoms may be modified by
treatment and obscured by extraneous influences. Subjective symptoms may be the
only evidence of physical disorder, as in pruritus, or may be entirely absent.
In most instances chief reliance is placed on objective characteristics of one
or more lesions which can be seen and felt.
Certain physiologic phenomena help to explain the symptomatology and
histopathology in some diseases. The more important are: Arthus' phenomenon,
which is a local edema and necrosis following the repeated subcutaneous
injection of a specific antigen in sensitized rabbits; Koebner's phenomenon,
which is the appearance of lesions of psoriasis or certain other skin diseases
at the site of an injury; and Shwartzman phenomenon, which is a severe
hemorrhagic reaction with necrosis seen in rabbits which are first injected
with typhoid or other culture filtrates into the skin and then twenty-four
hours later are injected intravenously with the same filtrate. The injected
area turns blue at the center and red at the periphery, the skin is smooth,
glossy and edematous. Histologic examination shows that the blood vessels below
the surface are ruptured and the numerous leukocytes are dead.
Subjective Symptoms
These consist of itching, sensation of heat or cold,
burning, tingling, prickling, stinging, biting, formication, and pain.
Itching, which is the most common of the subjective symptoms, varies in
degree and type. It may be a mere prickling or tingling, or its severity may be
so intense as to be intolerable. Itching may be spasmodic or continuous, and
may occur in paroxysms. It is commonly associated with eczema, urticaria,
dermatitis venenata, dermatitis herpetiformis, scabies, lichen planus, mycosis
fungoides, and pediculosis; it is also encountered more or less in all
inflammatory dermatoses, in xerosis, in metabolic disorders, carcinoma,
lymphoblastoma and nervous states. Pain is not of so common occurrence; it may
be boring, as in herpes zoster, shooting, as in tabes dorsalis, or throbbing,
as in boils and carbuncles.
Hypesthesia, anesthesia and hyperesthesia may
also be experienced by the patient. Such symptoms are, however, of uncertain
diagnostic nature unless corroborated by tests.