How does one diagnose psoriasis of the nails? What is the best treatment?
—R.K. Crisssman, MD, Grand Rapids, Mich.

Psoriasis of the nails can be clinically recognized by the presence of nail pits, onycholysis, and subungual hyperkeratosis. A common finding is the oil-drop or salmon-patch of the nail bed. This translucent, yellow-red discoloration in the nail bed resembles a drop of oil beneath the nail plate. It is the most diagnostic sign of nail psoriasis. Psoriatic nail disease can also occur with onychomycosis and paronychia. In addition, a nail-plate biopsy will often show histologic signs of psoriasis; if not, this biopsy can at least rule out onychomycosis.

No curative treatment for nail psoriasis exists at the present time. Onychomycosis (if present) requires antifungal therapy for improvement. The treatment options for nail psoriasis include topical corticosteroids, intralesional corticosteroids, psoralen plus UVA, topical fluorouracil, topical calcipotriol solution, topical anthralin, topical tazarotene, avulsion therapy, and systemic therapy for severe cases. For preventive care, one should keep the nails dry and protect them from trauma to avoid the Koebner (isomorphic) effect. In areas of onycholysis, the nail plate should be trimmed to the point of separation for medications to be effective.
—Jeffrey M. Weinberg, MD (100-18)