Can you identify this pruritic eruption?

Dermclinic
A Photo Quiz to Hone Dermatologic Skills 

Case: A pruritic eruption on his waistline of 3 weeks’ duration sent a 67-year-old man to his physician. Methylprednisolone was prescribed, but it relieved the symptoms only temporarily. He had recently completed a course of trimethoprim-sulfamethoxazole for a urinary tract infection, which resolved; the rash was not affected by the course of therapy.

Which of the following do you suspect?

A. Contact dermatitis.

B. Tinea corporis.

C. Candidiasis.

D. Intertrigo.

E. Erythrasma.

(Answer and discussion on next page)

 Answer: Tinea corporis

The results of a potassium hydroxide (KOH) evaluation confirmed the diagnosis of tinea corporis, B. The condition responded to antifungal therapy.

Typically, the failure of a rash to resolve following an adequate course of prednisone rules out contact dermatitis; however, this entity would have been considered if the patient’s KOH evaluation had been negative. (During the acute phase—6 weeks or less—contact dermatitis could be considered even if it failed to respond to corticosteroid therapy. However, it would be unusual for contact dermatitis not to respond unless contact with the culprit agent persisted.)

Candidal infection and intertrigo would not appear on the waistline but in the intertriginous folds. Erythrasma is a diagnosis of exclusion that is confirmed if the patient responds to antibacterial therapy.