詳しくは ― 日本人

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.

Parapsoriasis, presented as an early stage of cutaneous T-cell lymphoma, is mostly treated with psoralen and ultraviolet A (PUVA) therapy and narrowband ultraviolet B (NB-UVB) phototherapy.