Using whole-exome sequencing, we identified a c.1367delG mutation(p.Arg456fs) in CHST15 (NM_001270764), a gene encoding a type II transmembraneglycoproteinthat acts as a sulfotransferase and participates in the biosynthesis of chondroitin sulfate E, in germline and somatic cells in familial MPN. The gene discussed is CHST15; the disease is myeloproliferative disorder.