Causes and outcomes of hypereosinophilia in a tropical country

Abstract

Background: Hypereosinophilia (HE), defined by blood eosinophils > 1.5 ? 109/L persisting over one month, is commonly found in clinical practice.

Objective: This study aimed to explore etiologies, clinical characteristics, and outcome of HE.

Methods: The HE patients from a single center in Thailand during 2014-2019 were retrospectively reviewed.

Results: Among 166 HE patients, 102 (61.5%) cases had reactive HE (HER) of which 52% was due to parasitic infestations. Two-thirds of these patients were diagnosed based on the patients' response to empirical anti-parasite therapy. Without secondary causes, eosinophil-related symptoms were found in 20 (12.0%) patients (Hypereosinophilic syndrome: HES) of which three of them had myeloid neoplasms (HESN) and one case had lymphocytic variant HES (L-HES). Among 11 of 16 idiopathic HES (HESI) patients who were treated with systemic steroid, nine (81.8%) patients responded well, and two cases obtained symptom improvement with stable eosinophilia. There was 44 (26.5%) asymptomatic HE of undetermined significance (HEUS) and 37 (84.1%) of them had HE for more than 6 months before diagnosis. Marked eosinophilia (> 10 ? 109/L) was more common in HES (37.5%), but it was also found in HER (16.7%) and HEUS (11.4%). During the median follow-up period of 16 months, 82.9% (34/41) of HEUS cases remained asymptomatic while seven (17.1%) patients spontaneously recovered.

Conclusions: A therapeutic trial of anti-parasite is reasonable for asymptomatic HE in tropical countries. Most HESI responded to systemic corticosteroids and HEUS showed benign courses without therapy.