Dermatologic diseases of the nail unit other than psoriasis and lichen planus.

Diseases in which involvement of the nails may be helpful in the diagnosis of dermatologic disease elsewhere include psoriasis, lichen planus, Darier's disease, alopecia areata and totalis, keratotic scabies, scleroderma, and lupus erythematosus and dermatomyositis. Dermatologic diseases in which involvement of the nail commonly occurs but is relatively nonspecific and not diagnostic include dermatitis, lichen striatus, parakeratosis pustulosa, pityriasis rubra pilaris, acrokeratosis paraneoplastica, pemphigus vulgaris, epidermolysis bullosa, porokeratosis of Mibelli, and acanthosis nigricans. These entities are described and treatments summarized as appropriate.