A 6-year-old boy with fever and eosinophilia.

Tissue and blood eosinophilia can be associated with a variety of infectious, allergic, and systemic diseases. Eosinophilia can range from mild and clinically inconsequential levels to high-grade eosinophilia with severe and potentially fatal consequences. Because of its ability to degranulate and produce cytotoxic mediators such as major basic protein and eosinophil peroxidase the eosinophil has the potential to cause considerable tissue damage, including potentially fatal conditions such as endomyocardial fibrosis. The most common infectious cause of eosinophilia worldwide is the parasitic helminth; fungal infection as a cause of eosinophilia is rarer, but must also be considered in the differential diagnosis. In this article we describe a unique case of reactive eosinophilia.