The JAK2 46/1 haplotype in Budd-Chiari syndrome and portal vein thrombosis.

The germline JAK2 46/1 haplotype has been associated with the development of JAK2(V617F)-positive as well as JAK2(V617F)-negative myeloproliferative neoplasms (MPNs). In this study we examined the role of the 46/1 haplotype in the etiology and clinical presentation of patients with splanchnic vein thrombosis (SVT), in which MPNs are the most prominent underlying etiological factor. The single-nucleotide polymorphism rs12343867, which tags 46/1, was genotyped in 199 SVT patients. The 46/1 haplotype was overrepresented in JAK2(V617F)-positive SVT patients compared with controls (P < .01). Prevalence of the 46/1 haplotype in JAK2(V617F)-negative SVT patients did not differ from prevalence in the controls. However, JAK2(V617F)-negative SVT patients with a proven MPN also exhibited an increased frequency of the 46/1 haplotype (P = .06). Interestingly, 46/1 was associated with increased erythropoiesis in JAK2(V617F)-negative SVT patients. We conclude that the 46/1 haplotype is associated with the development of JAK2(V617F)-positive SVT. In addition, our findings in JAK2(V617F)-negative SVT patients indicate an important role for the 46/1 haplotype in the etiology and diagnosis of SVT-related MPNs, independent of JAK2(V617F), that requires further exploration.