JAK2 and myeloproliferative disorder: A search for the genetic basis of the predisposition to acquire MPN has revealed single nucleotide polymorphisms (SNPs) associated with MPN, for example the germline haplotype (GGCC, referred to as “46/1”) encompassing the 3’ region of the JAK2 gene is associated with a three- to four-fold risk of MPN (65).