Local varieties

It is customary to make certain local varieties; they are:

Psoriasis capitis. - The head is one of the commonest seats of the disease, next to the elbows and the knees; the whole scalp may be affected, or there may be only one or two small points of eruption; when extensive, the disease travels on to the forehead, forming a kind of fringe along it at the upper part. There is co-existent disease elsewhere. The hair on the scalp thins out frequently when psoriasis attacks it.

Psoriasis faciei. - In this local variety of psoriasis, the patches are often circular; they are less hyptaemic, less thick, and less scaly than when the disease attacks other parts of the body, and they present consequently much similarity to tinea circinata, except that typical patches of the disease are seen in other parts of the body.

Psoriasis palmaris and psoriasis plantatvt are important local varieties. These local varieties are infinitely rare. Of course, instances of so-called psoriasis palmaris and plan-taris are common enough, but they are practically always syphilitic. Non-syphilitic psoriasis may occur, though rarely, in connection with general psoriasis. But when such a condition exists as the sole disease, it is syphilitic and nothing else, and the concomitance of sore tongue and other evidences of constitutional syphilis at once make the diagnosis certain. The skin in the affected parts is generally thick, and dry, harsh, discolored; the scaliness is not very marked, but the superficial layers peel off from time to time. Presently the surface cracks and fissures, and healing is very tardy; occasionally the surface bleeds. The muscular movements of the hand may be painful.


Psoriasis unguinum is mostly a complication of the inveterate form of psoriasis, but it may exist alone. The nails (and several are usually affected) lose their polish, and soon become opaque, thickened, irregular, and brittle; they are then fissured and discolored in lines (from dirt), their matrix becoming scaly.


Psoriasis also affects the scrotum and prepuce occasionally; the parts are swollen, red, hard, tender, scaly, fissured more or less, and give exit to a thin secretion, which adds to the scaliness; there are pain and pruritus; and the local mischief may be the sole, or part only, of general disease. Psoriatic syphilides. - Nozo asserts that psoriatic syphi-lides always indicate the presence of a grave variety of syphilis and that they occur most commonly in cachectic subjects. In some cases they may appear as late manifestations of the disease; and their development is favored by old age, alcoholism, congenital or acquired dryness of the skin, and perhaps, also, by gout. Cases occur concerning which even the most expert diagnostician may be in doubt as to whether the eruption is the ordinary psoriasis or a specific eruption.

When psoriasis is in progress of cure, the scales lessen and the reddened elevated surface beneath comes more prominently into view; but this diminishes gradually till the eruption disappears, leaving oftentimes no trace of its former presence behind. It may leave, however, pigmentary stains, the result of the congestion. It is in the disappearance of patches of psoriasis that the centre rapidly clear, and the ringed form or psoriasis circinata, or the lepra of old authors is produced.