Germline monoallelic SH2B3 variants were also found in some patients with familial MPN, myelodysplasia (MDS)/MPN-overlap syndrome with ring sideroblasts, chronic myelomonocytic leukemia, erythrocytosis and immune cytopenia [6, 7, 11–16]. The gene discussed is SH2B3; the disease is myeloproliferative disorder.