Hypereosinophilic syndromes

Background: The last few years have seen a complete change in the etiopathogenetic features, classification and therapeutic approach of the hypereosinophilic syndrome (HES), a multiorgan targeted blood disease. The discovery of a genetic mutation and the occurrence of a new fusion gene, named FIP1L1-PDGFRA (FIP gene), in some patients allowed the identification of a new myeloproliferative disorder, M-HES: thereafter, the pivotal therapeutic role of the tyrosine kinase inhibitors, particularly, imatinib mesylate, was clearly detected. In the same period a new pathogenetic mechanism has been detected: some authors described the presence of a CD3-CD4 +Tcell clone correlating with the overproduction of IL5, a potent eosinophilic cell line stimulating cytokine. As a consequence an international consensus committee proposed a new classification for these syndromes, in accordance with these new pathogenetic features. The disease is characterized by an extensive tissue and organ damage due to an eosinophilic cell infiltration and leading to the release of toxic cytokines and subsequent organ dysfunction. The heart, lungs, gastrointestinal apparatus, skin and central nervous system are affected. Moreover the released cytokines can induce a thrombophilic status and thromboembolic events can occur throughout the body.
Aim of the study: We describe the diagnostic procedures that are necessary in order to obtain a correct diagnosis and classification of the disease and to evaluate the presence of an organ and tissue damage. In particular, bone marrow biopsy and cytogenetic examination of blood and marrow are necessary for detecting M-HES cases that are positive for the FIP gene. In these patients, imatinib mesylate has a leading role for obtaining complete remission of the disease in a high percentage of cases. We also examine the therapeutic options for the other forms of the disease: prednisone, interferon, hydroxiurea are effective therapeutic tools in these patients. Finally, the new therapeutic perspectives, such as monoclonal antibodies directed against IL 5 or IL 5 receptor and novel tyrosine kinase inhibiting drugs, are examined.