PSORIASIS (LEPRA ALPHOS, ALPHOS, PSORIASIS VULGARIS)

Synonyms.   Lepra alphos, alphos, psoriasis vulgaris.

Psoriasis is a common chronic, recurrent, inflammatory disease of the skin characterized by rounded, circumscribed, erythematous, dry scaling patches of various sizes covered by grayish-white or silvery-white, im­bricated and abundant scales. The lesions have a predilection for the scalp, nails, extensor surfaces of the limbs and the sacral region. The eruption is usually symmetrical and may vary from a solitary spot to countless patches. The eruption usually develops slowly but may be exanthematic, with the sudden onset of numerous guttate lesions, or may consist of a few inveterate patches. Subjective symptoms such as itching or burning may occasionally be present. The cause of the disease is unknown.

The early lesions are guttate erythematous macules or maculopapules, which from the beginning are covered with dry silvery scales. By periph­eral extension and by coalescence, the spots increase in size, and through the accumulation of scales they become thicker. Nummular (coin-shaped) lesions are common. In this variety certain distinctive features may be easily demonstrated: (1) The scales are micaceous, and looser toward the periphery of the patch while adherent at the center; (2) upon re­moval of the scales, bleeding points occur. After the patches reach a diameter of about 5 cm., they cease spreading and tend to undergo in­volution in the center, so that annular, lobulated and gyrate figures are produced.

Old patches may be thickened and tough, and covered with lamellae of scales so that they resemble the outside of an oyster shell (psoriasis ostracea). Various other descriptive terms are applied to the diverse ap­pearances of the lesions: psoriasis guttata, in which the lesions are the size of drops; psoriasis follicularis, in which tiny scaly lesions are located at the orifices of the pilosebaceous follicles; psoriasis figurata, psoriasis annulata, and psoriasis gyrata, in which curved linear patterns are pro­duced by central involution; psoriasis discoidea, in which central involu­tion does not occur and solid patches persist; psoriasis rupioides, in which crustaceous lesions occur resembling syphilitic rupia; psoriasis arthro-pathica, a particularly inveterate form associated with chronic arthritis. This is a polyarthritis of the small joints of the hands and feet.

Extensive cases of long duration may develop a universal erythroderma. In a review of over 2200 cases of psoriasis, Coeckerman and O'Leary were able to find 22 cases (about 1 per cent) of erythroderma psoriaticum. Auto-sensitization may account for this universal exfoliative erythroderma. Rarely, bullous lesions have been observed during acute exacerbations, and cases have been reported in which generalized eruptions of flaccid bullae later developed features characteristic of psoriasis. Pustular psoriasis was described by Schaffer in 1921 and later by MacLeod. The typical psoriatic patches become covered with small pustules. This change sometimes pre­cedes the development of generalized exfoliative dermatitis. Pustular psoriasis of the extremities, as described by Barber and Ingram, is a differ­ent clinical expression of the disease, which is considered separately. Flexural psoriasis is a definite regional type.

The course of psoriasis is inconstant. It usually begins on the scalp or on the extensor surfaces of the elbows, and may remain localized to the original region for an indefinite period, or completely disappear, recur, or spread to other parts. The beginning may be over the sacrum, where the patch slowly extends to form an inveterate lesion. At other times the onset is more sudden and widespread, as already described; or in other cases the first lesions may be limited to the fingernails.

One of the chief features of psoriasis is its tendency to recurrences. These are commonly manifest over and over again throughout the life­time of the patient. Rarely, however, psoriatics may remain completely free of the disease for years, and may be considered, in at least a practical sense, cured. On the scalp it does not cause loss of hair. The lesions are sometimes easily irritated—even the chronic ones—and when this takes place they are liable to spread by the development of satellites, or new spots in other regions. In acute guttate or nummular spreading eruptions, if irritat­ing remedies arc applied, a generalized exfoliative dermatitis may result. Although psoriasis affects both children and adults, the course of the disease is comparatively mild in children.

The Koebner phenomenon is the appearance of typical lesions of psori­asis at sites of injuries. Tins is a characteristic feature of the disease and accounts for the frequent appearance of typical psoriatic patches on scars and at sites of operations and burns. Occasionally the initial patch is upon the site of such a trauma. In the presence of early lesions, new lesions can be produced by scratching the skin. The Koebner phenomenon occurs in many other skin diseases, such as lichen planus, lichen nitidus, verruca plana and infectious eczematoid dermatitis.

The various theories concerning the etiology of psoriasis are too volu­minous to be covered adequately in the space permitted. Present tendencies favor a metabolic disturbance of phosphorylation, often inherited, which may be influenced by stress and focal infection. There is a history of family incidence in about 25% of the cases. The frequent association of this combination of factors with arthritis is noteworthy.