How would you diagnose this 5-year itch?

A 33-year-old male presented with an over 5-year history of a slightly itchy eruption confined to the trunk that had failed topical corticosteroid therapy years earlier.

How would you diagnose his itch?

A.  Pityriasis rosea

B.  Tinea versicolor

C.  Psoriasis

D.  Parapsoriasis

E.  Secondary syphilis

(Answer and discussion on next page)

Answer: Parapsoriasis

A biopsy confirmed the clinical impression of small plaque parapsoriasis. This is a benign condition of unknown etiology and can run a protracted course over years. Ultraviolet light therapy is often an effective treatment. Tinea versicolor would be expected to have more scales. Pityriasis rosea should not last this long nor should secondary syphilis. Psoriasis should have more scales and is usually itchy.