Parapsoriasis describes a group of cutaneous diseases that can be characterized by scaly patches or slightly elevated plaques that have a resemblance to psoriasis, hence the nomenclature. However, this description includes several inflammatory cutaneous diseases that are unrelated with respect to pathogenesis, histopathology, and response to treatment. Because of the variation in clinical presentation and a lack of a specific diagnostic finding on histopathology, a uniformly accepted definition of parapsoriasis remains lacking.
In 1902, Brocq initially described 3 major entities that fit the description:
Pityriasis lichenoides (acuta and chronica)
Small plaque parapsoriasis
Large plaque parapsoriasis (parapsoriasis en plaque)
