Parasitic infections, most commonly with such tissue-invasive helminths as filariae and Strongyloides , Trichinella , Schistosoma , and Toxocara species, frequently present with eosinophilia. In addition, serologic assays, radiologic tests, and peripheral blood and bone marrow smears should be performed to exclude the presence of connective tissue diseases, occult lymphoproliferative syndromes and solid tumors, and hematologic malignancies, respectively. The bone marrow is usually hypercellular, with eosinophils constituting 25 to 75 percent of the marrow elements. However, these cardiac changes are not distinguishable from those found in patients with secondary eosinophilia. Patients may have chronic congestive heart failure, valvular abnormalities, and distinctive, fibrous, biventricular endocardial thickening with mural thrombi.
Most patients show thickening of the left ventricular wall.
The echocardiogram is the most sensitive method of detecting these cardiac abnormalities. Pulmonary involvement in HES may also occur and results in fever, cough, weight loss, and wheezing. The diagnostic approach to a person suspected of having HES should include a complete history and physical examination, a complete blood count, and a total eosinophil count. If the patient is diagnosed with HES, the decision to administer therapy should be based on the presence or absence of symptoms. If no symptoms are present, no treatment is instituted and the patient is reevaluated periodically.