Clonal Th2 lymphocytes in patients with the idiopathic hypereosinophilic syndrome

Idiopathic hypereosinophilic syndrome (HES) and Gleich's syndrome are related disorders characterized by persistent or recurrent hypereosinophilia of unknown origin. Elevated IgE levels and polyclonal hypergammaglobulinaemia are considered as markers of benign outcome in this setting as they are generally associated with predominant cutaneous manifestations and favourable response to glucocorticoid therapy. In a previous study, we identified a clonal population of CD3-CD4+ Th2-like lymphocytes secreting interleukin (IL)-5 and IL-4 in peripheral blood of a patient fulfilling the diagnostic criteria of HES with associated serum hyper-IgE. We now extend this observation by describing identical findings in three additional patients, and we compare their clinical and biological parameters with five other patients with HES. Chromosomal abnormalities were detected in purified CD3-CD4+ Th2 cells from three patients, among whom one developed anaplastic null cell lymphoma. We therefore suggest that a careful search for T-lymphocyte clonality and cytogenetic changes should be included in the work-up of HES for adequate management.