A 7-year-old male presents to your office for an abrupt onset of pruritic papules on the extremities pictured below. 

Which is the most common culprit of this rash in the United States?

A. Influenza

B. CMV

C. EBV

D. Hepatitis B

E. Hepatitis C

Rationale: Gianotti-Crosti syndrome, also known as papular acrodermatitis of childhood, presents as an acute eruption of flat-topped papules or papulovesicles on the extensor surfaces of the extremities, buttocks, and face with sparing of the flexural surfaces. It tends to affect children and patients with atopic dermatitis are at higher risk of developing this eruption. Differential diagnoses include hand, foot, and mouth disease, papular urticaria, IgA vasculitis, lichen planus, and molluscum contagiosum. The eruption is self-limited and tends to fade over a period of 3-4 weeks.  

Correct answer:

Gianotti-Crosti syndrome is typically associated with a viral infection but has also been reported with immunizations. Of the options, EBV is the most common cause in the United States. Another image if Gianotti-Crosti is shown below.

Incorrect answers:

CMV, influenza, Hepatitis B, and Hepatitis C, have all been associated with Gianotti-Crosti syndrome. Worldwide immunization efforts have decreased the number of cases associated with Hepatitis B. Several other viruses have been associated with this eruption as well. 

Additional reading at Fitzpatrick's Dermatology Chapter 163: Exanthematous Viral Diseases