JAK2 and myeloproliferative disorder: Multiple studies have demonstrated that besides the somatic mutation(s), there is a substantial hereditable component, linked to the risk of MPN[3–5], and germline variations in JAK2 itself, such as the JAK2 GGCC haplotype, have been associated with JAK2-V617F somatic mutation acquisition and the development of MPNs [6, 7].