Which clues point to the cause of this pruritic rash?

A pruritic rash of a few months’ duration on the palmar surfaces of both hands prompts a 43-year-old woman to seek medical care.

Which of the following are helpful diagnostic clues—and why?

A. Involvement of palmar versus dorsal surfaces.   
B. Pitted fingernails.   
C. Involvement of particular fingers.
D. Coexisting rash on the feet.
E. Small vesicles on the sides of the fingers (pompholyx).

Answer: Contact dermatitis

This patient has a contact dermatitis. The symmetrical involvement of the palmar surface, A, and of the particular fingers (the first three fingers), C, were helpful diagnostic clues.

The absence of nail pits helped rule out psoriasis. The patient did not have tinea pedis, which eliminated the possibility of an id reaction. Dyshidrosis, or pompholyx, is a nonspecific finding and is not helpful.

Patch testing identified the offending agent. The patient avoided the contactant, and the dermatitis cleared.