Low burden of a JAK2-V617F mutated clone in monoclonal haematopoiesis in a Japanese woman with Budd-Chiari syndrome.

Approximately one-half of the cases of Budd-Chiari syndrome (BCS) are caused by bcr/abl negative chronic myeloproliferative disorders (CMPDs). Furthermore, a mutation in the Janus kinase protein (JAK2-V617F) is detected in half of the patients with BCS. However, whether the JAK2 mutation is the primary event leading to CMPDs and BCS is controversial. We present a report concerning a young woman who suffered from BCS prior to the onset of CMPDs. Analysis of X-chromosome inactivation patterns in this patient, using the human androgen receptor gene demonstrated monoclonal haematopoiesis in her granulocytes. In contrast, she had a low burden of a JAK2-V617F mutation positive clone among granulocyte populations. These results suggest that the JAK2-V617F mutation occurs after the onset of monoclonal haematopoiesis; thus the V617F mutation of JAK2 may not be the primary event in the induction of BCS.