Eosinophilia of the blood. A search for the cause uncovers squamous cell carcinoma.

When laboratory evaluation uncovers eosinophilia of the blood, an extensive investigation is sometimes required to identify the cause. Parasitic infections and neoplastic, idiopathic, and collagen vascular diseases have been linked to abnormally high blood concentration of eosinophils, as have allergic reactions and adrenal insufficiency. Treatment should be directed at the underlying cause once it has been identified. The case discussed here was particularly interesting and unusual because the patient had nonspecific symptoms and marked eosinophilia of the blood, but initial laboratory test results and physical examination findings did not offer any diagnostic clues.