• Clinical science

Parapsoriasis

Summary

The term “parapsoriasis” covers a large group of idiopathic cutaneous diseases characterized by asymptomatic or mildly pruritic, erythematous, scaly patches, and a chronic course. The condition is roughly classified into two types: large plaque parapsoriasis and small plaque parapsoriasis. Large plaque parapsoriasis is considered a premalignant condition that can progress to mycosis fungoides. Diagnosis is based on clinical examination and histopathological findings on biopsy. Treatment includes topical steroid therapy and phototherapy.

Epidemiology

  • Rare disorder
  • Sex: >

References:[1][2][3]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

  • Group of cutaneous diseases of unknown etiology
  • Skin lesions (i.e., papules, patches, or plaques) caused by T-cell infiltration into the skin

The term “parapsoriasis” has its roots in its dermatological similarity to psoriatic lesions (e.g., plaques and scaly patches) seen during efflorescence.

References:[2]

Small plaque parapsoriasis

  • Clinical features
    • Round or oval, scaly, salmon-colored or yellow-brown patches
      • Size: < 5 cm diameter
      • Location: trunk, flanks, proximal extremities in non-sun exposed areas
    • Benign; chronic course (months to years); resolves spontaneously
  • Diagnostics: Skin biopsy
  • Treatment

References:[1][2][3][4]

Large plaque parapsoriasis

References:[2]

Differential diagnoses

References:[2]

The differential diagnoses listed here are not exhaustive.