Underlying eosinophil-related diseases included FIP1L1-PDGFRA-associated chronic myeloid neoplasm (n = 4), Eosinophilic Granulomatosis with Polyangiitis (n = 9), lymphocytic (n = 1) and idiopathic (n = 29) variants of hypereosinophilic syndrome. The gene discussed is FIP1L1; the disease is hypereosinophilic syndrome.