How would you treat this pruritic rash?

This slightly itchy rash had slowly spread over a 37-year-old man’s trunk during the past month. The patient is otherwise healthy and denies the use of any new medications, soaps, or detergents.

Can you identify this rash?

A. Pityriasis rosea. 

B. Tinea versicolor.

C. Drug reaction.

D. Tinea corporis.

E. Mycosis fungoides.  

(Answer on next page)

Answer: Tinea versicolor

This rash looks like tinea versicolor, B. A potassium hy- droxide (KOH) evaluation was therefore performed.

A drug reaction would have been a reasonable sus- picion, but it was not supported by the history. Mycosis fungoides has a more poikilodermatitic appearance— with atrophy and telangiectasia—than the rash seen here. Pityriasis rosea yields a negative KOH result. The KOH finding for tinea corporis, a dermatophyte infec- tion, reveals true-branched hyphae, whereas pseudohy- phae and spores are seen in the preparation of tinea versicolor scrapings.