Chronic eosinophilic leukemia-not otherwise specified (CEL-NOS) is a rare disorder with hypereosinophilia and an increased number of blood or marrow blast (<20%) or an evidence of eosinophil clonality. We evaluated the clinical outcome of 10 patients with CEL-NOS. Seven males and three females at a median age of 62 years (range, 23-73) were included. The median leukocyte count at diagnosis was 33.4 3 10 9 /l (range, 9.3-175.0) with a median eosinophil count of 15.6 3 10 9 /l (range, 1.5-136.0). Median hemoglobin and platelets were 11.0 g/dl (range, 8.3-13.3) and 158 3 10 9 /l (range, 31.0-891.0), respectively. Clinical manifestations included splenomegaly (n 5 7), hepatomegaly (n 5 6), cardiac failure (n 5 2), and lung infiltrations (n 5 1). Median survival from diagnosis to death for entire cohort was 22.2 months (range, 2.2-186.2). Five of the 10 studied patients developed acute transformation (AT) after median of 20 months from diagnosis (range, 1.6-41.9). None of patients with AT is alive at the time of last follow-up. Median time from AT to death was 2 months (range, 1.0-6.1). Among five patients who did not develop AT, three died in active disease. Two patients are alive in complete remission; first underwent allogeneic stem-cell transplantation preceding by intensive induction chemotherapy; the second remains on imatinib with hydroxyurea. Except the latter patient, imatinib was ineffective in our study population. CEL-NOS is a rare and aggressive disease with high rate of AT and resistance to conventional treatment.Chronic eosinophilic leukemia-not otherwise specified (CEL-NOS) is a rare Philadelphia-negative myeloproliferative neoplasm, which is due to clonal proliferation of eosinophil precursors. Peripheral blood hypereosinophilia (>1.5 3 10 9 /l), an increased number of myeloblasts in blood or marrow (<20%) or an evidence of eosinophil clonality, are required for diagnosis. The cases of myeloid and lymphoid neoplasms with abnormalities of platelet-derived growth factor alpha (PDGFRA), platelet-derived growth factor beta (PDGFRB), and fibroblast growth factor receptor 1 (FGFR1) must be also excluded [1]. In a new WHO classification, CEL-NOS is listed in the category of myeloproliferative neoplasms [2], whereas it was incorporated under the heading of myeloproliferative forms of hypereosinophilic syndromes according to the classification of the Eosinophilic Working Group [3]. Regardless of the classification used, CEL-NOS remains an extremely rare entity with variable prognosis [1,4]. The efficacy of currently used therapeutic agents is limited, and the hematological responses are usually short-lived [5].Ten patients (seven males and three females) at a median age of 62 years (range, 23-73) were included in this study. The median leukocyte count at diagnosis was 33.4 3 10 9 /l with a median eosinophil count of 15.6 3 10 9 /l. Blood smear was dominated by mature eosinophils with a small number of younger forms, for example, eosinophilic myelocytes and promyelocytes. Single eosinophils had dysplastic fe...

The idiopathic hypereosinophilic syndrome (HES) comprises a heterogenous group of disorders characterized by marked blood eosinophilia with eosinophilia-associated organ damage. Eight patients with a median age at diagnosis of 42 years (range 19-67) received imatinib mesylate (IM) for FIP1L1-PDGFRα-negative HES resistant to previous conventional treatment. Median number of prior therapies was 3 (range 2-4). Median time from diagnosis to IM initiation was 112 months (range 2-293). Four patients were treated daily with 100 mg IM, whereas the remaining four patients were treated daily with 400 mg IM. Four male patients (50%) achieved complete haematologic response (CHR) after median of 7 days (range 3-150) using 100 mg daily IM (n = 2) and 400 mg (n = 2). Median duration of IM treatment for IM responders was 18 months (range 2-88). No adverse events were reported throughout the treatment duration. Two patients maintained CHR while on 100 mg weekly IM. Four patients (2 men and 2 women) failed IM treatment. Median duration of IM for non-responding patients was 3 weeks (range 3-12). Non-responding HES patients were significantly older and had lower percentage of blood eosinophilia when compared with IM responders. Our results suggest that IM, even at lower than conventional doses, may induce and maintain long-term remission for FIP1L1-PDGFRα-negative HES.

The term “hypereosinophilia of undetermined significance” (HEus) previously known as idiopathic, benign eosinophilia relates to patients who have a long-lasting, unexplained and asymptomatic blood HE. These patients have not been studied so far in terms of demographic characteristics and clinical outcome. The aim of this study was to present the clinical characteristics and outcome of HEus patients. This is a retrospective, single-center study of 40 patients with HEus. All patients underwent the basic and specialized evaluations in order to rule out the most common causes of blood HE, but no abnormalities were detected. Twelve patients with at least moderate blood hypereosinophilia (defined as greater than 3.0 × 109/L) for more than 1-year duration were treated with corticosteroids (CS) to avoid end-organ damage. Twenty-one patients (52 %) had an increased leukocyte count at diagnosis. Median blood eosinophilia was 4.2 × 109/L (range 1.5–55.4). HE > 3.0 × 109/L was demonstrated in 17 patients. 65 % of studied population had an increased serum IgE levels, whereas only 2 % demonstrated an increased serum vitamin B12 levels. A median bone marrow infiltration by eosinophils was 30.5 % (range 11–78.2). All treated patients responded promptly to CS and remained in complete remission while receiving low doses of CS (20 mg/day to 5 mg every 2-day). One patient developed hypereosinophilic syndrome (HES) after 11 years of follow-up. Further studies are needed to define risk factors of HES development. The use of CS for HEus patients is controversial and should be individualized.

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