Urticarial lesions in a child with acute lymphoblastic leukemia and eosinophilia

The hypereosinophilic syndrome (HES) is defined by a longer than 6-month history of peripheral blood hypereosinophilia (greater than 1.5 x 10(9)/L), with signs and symptoms of internal organ involvement, in the absence of an identifiable cause. HES is therefore a diagnosis of exclusion. Patients have been reported who initially met the criteria for HES but subsequently developed a rare hematologic malignancy known as acute lymphoblastic leukemia with eosinophilia (ALL-Eo). We report such a case in a 10-year-old boy who presented to the pediatric dermatology clinic with unusual, urticarial skin lesions. Although skin involvement is often reported in cases of HES and ALL-Eo, such findings are variable and reports in the dermatology literature are few. We emphasize the importance of continuous monitoring for underlying malignancy in children with urticarial skin lesions in the setting of unexplained hypereosinophilia.