JAK2 and myeloproliferative neoplasm: Subsequently, in 2009, three independent groups revealed an interesting and strong association between the risk of developing a JAK2 V617F positive MPN and a germline haplotype including the 3′ portion of JAK2, named GGCC or 46/1 haplotype (haplotypeGGCC_46/1) [7,8,9].