Strongyloides IgE was negative, and bone marrow genetic tests on SCFD2, LNX, PDGFRA, PDGFRB, FGFR1, JAK2 V617F, CALR exon 9, JAK2 exon 12, MPL exon 10, and CSF3R exon 14/17 (genes associated with hypereosinophilic syndrome, eosinophilic leukaemia, and myeloproliferative neoplasms with eosinophilia) were all negative. Here, JAK2 is linked to hypereosinophilic syndrome.