Hypereosinophilia or HES are considered as neoplastic (or clonal or primary, HEN/SHEN) when an underlying myeloid/lymphoid/stem cell neoplasm with HE and rearrangement of PDGFRA, PDGFRB, FGFR or with PCM1-JAK2 translocation is identified. The gene discussed is PDGFRA; the disease is hereditary elliptocytosis.