Parapsoriasis is an uncommon inflammatory
skin disease characterized by chronic patches that may be resistant to
therapy. It was primarily introduced and classified 120 years ago, and the original classification incorporated
parapsoriasis and
pityriasis lichenoides under the umbrella term
parapsoriasis. After a major change in classification,
parapsoriasis now exclusively refers to small plaque
parapsoriasis (SPP) and large plaque
parapsoriasis (LPP). However, debates still frequently occur regarding various nomenclatures and classifications used by different authors. Moreover,
parapsoriasis may progress to overt cutaneous
lymphoma, most commonly
mycosis fungoides (MF), and it is very difficult to distinguish these two conditions despite modern histologic and molecular testing techniques.As
parapsoriasis is a
rare disease, there is a lack of studies and clinical guidelines to assist physicians in clinical practice. In our comprehensive review, we review several aspects of
parapsoriasis, from the history of nomenclature and classification, clinical characteristics, immunohistopathology, and advanced molecular techniques for the diagnosis of this condition, to the most current treatments. We also propose a scheme for distinguishing
parapsoriasis from early-stage MF in this review.