Why has this rash resisted corticosteroids?

Dermclinic
A Photo Quiz to Hone Dermatologic Skills 

Case: For 9 days, a 48-year-old woman has had a pruritic eruption on the right side of the trunk. Her condition was initially diagnosed as contact dermatitis, and prednisone, 20 mg/d, was prescribed. She has taken the medication for the past 3 days, but it has had no effect on the rash. She is otherwise healthy and had recently been working in her yard.

What does this look like to you?

A. Herpes zoster.

B. Herpes simplex.

C. Poison ivy dermatitis.

D. Unilateral pityriasis rosea.

E. Folliculitis.

(Answer and discussion on next page)

ANSWER: Poison ivy dermatitis

The patient has poison ivy dermatitis, C. The “dermatomal” pattern is the area that had come into contact with the plant. The prednisone dosage was too low to be effective. (A typical dosage in this setting is 1 mg/kg tapered over the course of 8 to 10 days.)

Herpes zoster can be pruritic in this patient’s age group but, as with herpes simplex, one would expect to see grouped vesicles. Pityriasis rosea usually has more scale. Folliculitis more closely resembles acne.