Psoriasis unguinum

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.