Juvenile xanthogranuloma: A herald to the diagnosis of Erdheim-Chester disease in an adult with acute leukemia.

A 21-year-old man with B-cell acute lymphoblastic leukemia developed an eruption of multiple flesh-colored nodules and persistent fevers. A lesional biopsy showed diffuse dermal infiltrates of histiocytes, foam cells, and Touton giant cells consistent with juvenile xanthogranulomatosis. Upon further investigation, the patient's constellation of findings fit criteria for Erdheim-Chester disease.