One lab finding, 2 vastly different causes

DISCUSSION

These 2 cases highlight how the presentation of eosinophilia can vary and how important it is to maintain a broad differential diagnosis (TABLE 1^1-4). Causes of eosinophilia are numerous and can be divided into 3 categories: primary, secondary, and idiopathic.^1,5 Hematologic malignancy, where eosinophilia is clonal, is an example of a primary etiology. Causes of secondary eosinophilia include infectious diseases, drugs (TABLE 2⁵), autoimmune disorders, and allergic conditions. Prolonged eosinophilia that is >3 x 10⁹/L is associated with end-organ damage. Dermatologic, pulmonary, gastro­intestinal, and cardiac involvement is most common.²

Eosinophilia associated with parasitic infection

In returning travelers and international adoptees, multicellular helminthic parasites are the most common causes of eosinophilia, with eosinophilia occurring during tissue migration or penetration.^1,3