Hypereosinophilic Syndrome as a Rare Cause of Reversible Biventricular Heart Failure.

Hypereosinophilic syndrome is a rare entity that can develop secondary to overproduction of eosinophilopoietic cytokines or as idiopathic disease. Cardiac involvement, which occurs often, is divided into 3 stages, the latter of which is nonreversible and leads to severe heart failure. Early detection and treatment of the syndrome is essential. For this reason, genetic testing for the FIP1L1-PDGFRA fusion gene has recently been added to the diagnostic algorithm. Patients with this mutation are at increased risk for the development of cardiac involvement and typically respond to treatment with the tyrosine kinase inhibitor imatinib mesylate.