What clues in the history point to the cause of this itchy, scaly eruption?

Is this scaly rash a drug reaction-or something else?

What caused this intensely pruritic eruption?

How do you explain this asymptomatic rash on a woman’s breast?

Case 4:

For several weeks, a 25-year-old man has been bothered by a pruritic rash on his hands. He has a history of allergies but is otherwise healthy. He owns 2 dogs.

What is your clinical impression?

A. Scabies.
B. Dog scabies.
C. Atopic dermatitis.
D. Contact dermatitis.
E. Lichen planus.

(answer on next page)

Case 4: Dyshidrosis that resembles scabies

This young man had a flare of atopic dermatitis, C, which manifested itself as a dyshidrotic hand eczema. Potent topical corticosteroids relieved the symptoms, but the cause of the flare could not be identified. The scabies preparation was negative.

Scabies would be expected to spread beyond the hands and wrists. Similarly, dog scabies would not be confined to the hands. Contact dermatitis can present as a dyshidrotic reaction, which may require patch testing to try to establish the cause. Lichen planus is characterized by purple, flat-topped, polygonal papules that do not resemble the rash seen here.