Papulosquamous diseases: a review.

Papulosquamous diseases are a heterogeneous group of disorders whose etiology primarily is unknown. The nosology of these disorders is based on a descriptive morphology of clinical lesions characterized by scaly papules and plaques. The major entities in this group include psoriasis, parapsoriasis (including pityriasis lichenoides et varioliformis acuta), lichen planus, lichen nitidus, lichen striatus, pityriasis rosea, pityriasis rubra pilaris, seborrheic dermatitis, and the Gianotti-Crosti syndrome. Many other conditions may become papulosquamous and should be considered in the differential diagnosis.