What would you say about this boy’s rash?

David L. Kaplan, MD—Series Editor

This 3-year-old boy presented with a 1-week history of an asymptomatic rash on the trunk and extremities. The rash had been preceded by an upper respiratory infection, which the child’s pediatrician had treated with a 1-week course of amoxicillin. The patient had no known drug allergies and was in good health, except for the rash. He did not have a history of rashes in the past. His immunizations were up-to-date.

Gianotti-Crosti syndrome

What would you say about this boy’s rash?

  1. This is a delayed drug reaction to the amoxicillin.
  2. This is a delayed viral exanthem related to the upper respiratory infection.
  3. This is a flare of atopic dermatitis precipitated by the upper respiratory infection.
  4. This is the onset of atypical measles syndrome, despite the patient’s having been vaccinated for measles.
  5. These lesions are bed bug bites.


Answer on next page.


Gianotti-Crosti syndrome

Answer: Delayed viral exanthem (Gianotti-Crosti syndrome)

The appearance of an asymptomatic, flat, papular eruption appearing predominantly on the extensor surfaces of the extremities is consistent with Gianotti-Crosti syndrome, or papular acrodermatitis of childhood. 

This reactive process has been associated with several infectious agents and immunizations. It can run a protracted course over several weeks before spontaneously disappearing. 

No etiologic treatment is necessary for Gianotti-Crosti syndrome, and the condition typically is treated symptomatically.

Lesions associated with drug reactions are typically more generalized and are pruritic. Atopic flares would be expected to occur in the flexural folds and to be pruritic, and they generally occur in patients with a history of eczema. Atypical measles are extremely rare, and the patient would have the symptomatology of viremia. Bed bug bites are generally not this extensive, are pruritic, and are more common on exposed areas of skin.

David L. Kaplan, MD, is a clinical assistant professor of dermatology at the University of Missouri–Kansas City School of Medicine in Kansas City, Missouri, and at the University of Kansas School of Medicine in Kansas City, Kansas. He practices adult and pediatric dermatology in Overland Park, Kansas.