The hypereosinophilic syndrome and lymphoblastic leukemia with extra C-group chromosome and q14+ marker

Hypereosinophilic syndrome is probably a disease of diverse etiologies. We studied the bone marrow of a patient with HES and found a population of L-1 lymphoblasts. These cells failed to grow in double-layer agar cultures, were "null cells," and contained a 14q+ marker chromosome consistent with a malignant lymphoproliferative disorder. Complete remission was induced with vincristine, prednisone, and L-asparaginase but the patient died from the consequences of cardiac fibrosis. An underlying lymphoproliferative process should be carefully sought in patients with HES to afford the best opportunity for cure.