Further work up for tissue eosinophilia and persistent blood eosinophilia included exclusion of neoplasia, vasculitis, ischemia, hypereosinophilic syndrome, systemic or parasitic infection by bone marrow histology, various analyses for gene mutations (FIP1L1-PDGFR, JAK 2 V 617 F, BCR-ABL rearrangement and other mutations), multiple stool cultures, various autoantibodies as well as viral and bacterial serology. This evidence concerns the gene JAK2 and Increased total eosinophil count.