Malignancy Is the Most Common Cause of Severe Eosinophilia in the Northeastern U.S.

Untreated, severe eosinophilia (i.e., absolute eosinophil count >5000 cells/μL) can result in organ damage, which makes prompt recognition and treatment of the underlying cause a high priority. In this case series, researchers report underlying causes of severe eosinophilia among 193 patients at two academic medical centers in the northeastern United States.

The most common causes of severe eosinophilia were hematologic and solid-organ malignancies, which collectively were diagnosed in 39% of cases (the authors included 7 cases of idiopathic hypereosinophilic syndrome in this category). Among these, hematologic malignancies (most commonly, chronic myelogenous leukemia) accounted for 60%. The second most common category was drug reactions (20…