Israel Medical Association Journal

Paraneoplastic syndromes are reported in 8–15% of patients diagnosed with cancer [1]. They are defined as syndromes that occur due to an underlying malignancy, which has yet to be diagnosed, or at the time of the diagnosis and less frequently following the diagnosis of a malignancy. Several mechanisms are involved including autocrine and paracrine mediators, hormones, peptides, cytotoxic lymphocytes, and cytokines [1,2].

Hypereosinophilia is defined as the absolute eosinophilic count of above 1500 cells/µL in the peripheral blood on two separate tests taken during one month and/or the pathological confirmation of hypereosinophilia. There are many conditions that are associated with increased eosinophil counts including: parasitic infections, drug reactions, eosinophilic granulomatosis with polyangiitis, allergic reactions, drug reaction with eosinophilia and systemic symptoms (DRESS), primary immunodeficiencies (PID), eosinophilic gastrointestinal diseases (EGID), familial hypereosinophilia, and neoplasms [1]. Molecular classification may be an adjuvant in the classification of hypereosinophilia [2]. Our patient presented with hypereosinophilia as part of a paraneoplastic syndrome.