Abbreviations:JAK2 = Janus kinase 2 gene, PMF = primary myelofibrosis, MPNs = myeloproliferative neoplasms, ET = essential thrombocythemia, PV = polycythemia vera, MM = multiple myeloma, WBC = white blood cells, Hb = haemoglobin, Ht = haematocrit, Plt = platelets, BMB = bone marrow biopsy, CBC = blood cell count, CT = computerized tomography, LAP = leukocyte alkaline phosphatase, MGUS = monoclonal gammopathy of undetermined significance. The gene discussed is GSTM1; the disease is Miyoshi myopathy.