Hypereosinophilic syndrome and mepolizumab

Safety of Mepolizumab in Immigrant Populations

One safety concern for mepolizumab’s use, beyond a clinical trial, is the importance of excluding occult parasitic infections, most importantly Strongyloides stercoralis. Suppression of eosinophilia with corticosteroids causes life-threatening strongyloides hyperinfection (1). Whether anti-interleukin-5 therapy holds this same iatrogenic mortality risk is unknown, but probable. One in 8 Americans are foreign-born and >50–75% of immigrants with asymptomatic eosinophilia will have a parasitic infection (2). Seybolt et al. found 12% of arriving refugees had eosinophilia, and although 71% had negative stool ova and parasite examinations, 39% and 22% had serologic evidence of strongyloidiasis and schistosomiasis, respectively, when tested (2). In Sudanese refugees, rates were 46% and 44% (3). We have reported that practicing U.S. physicians and physicians-in-training have poor knowledge of strongyloidiasis which places immigrants at iatrogenic risk (4). Since standard stool examination is notoriously insensitive (≤50%) for detecting strongyloides, serologic screening or presumptive treatment is often necessary (4,5). Before therapy for hypereosinophilia, all persons with previous exposure must be tested for parasites commonly causing chronic infections and eosinophilia such as strongyloidiasis, schistosomiasis, and filariasis.