How I treat hypereosinophilic syndromes

Abstract

Hypereosinophilic syndromes (HESs) are a group of rare disorders characterized by peripheral blood eosinophilia of 1.5 × 10(9)/L or higher and evidence of end organ manifestations attributable to the eosinophilia and not otherwise explained in the clinical setting. HESs are pleomorphic in clinical presentation and can be idiopathic or associated with a variety of underlying conditions, including allergic, rheumatologic, infectious, and neoplastic disorders. Moreover, the etiology of the eosinophilia in HESs can be primary (myeloid), secondary (lymphocyte-driven), or unknown. Although corticosteroids remain the first-line therapy for most forms of HESs, the availability of an increasing number of novel therapeutic agents, including tyrosine kinase inhibitors and monoclonal antibodies, has necessarily altered the approach to treatment of HESs. This review presents an updated treatment-based approach to the classification of patients with presumed HES and discusses the roles of conventional and novel agents in the management of these patients.

Figure 1

Treatment-based approach to HESs. Algorithms are proposed for evaluation of (A) presumed HES, (B) clinically stable HES, and (C) steroid-resistant HES. *M-HES is defined for the purposes of this algorithm as HES with a genetic abnormality known to cause clonal eosinophilia or idiopathic HES with ≥4 of the following features: dysplastic eosinophils, serum B₁₂ >737.8 pM (1000 pg/mL), serum tryptase >12 ng/mL, anemia and/or thrombocytopenia, splenomegaly, bone marrow cellularity >80%, myelofibrosis, spindle-shaped mast cells >25%, or strong clinical suspicion of a myeloproliferative disorder.

Figure 2

Frequency distribution of diagnoses in a cohort of 302 subjects referred for evaluation of unexplained hypereosinophilia.