The recent discovery of exon 9 insertion and/or deletion mutations of the CALR gene in up to 80% of JAK2- and MPL-unmutated essential thrombocythemia and primary myelofibrosis patients compels the incorporation of CALR mutational analysis into the molecular diagnostic algorithm for these myeloproliferative neoplasms (MPN). MPN are a major cause of splanchnic vein thrombosis (SVT) which encompasses Budd-Chiari syndrome, portal and mesenteric vein thrombosis. Up to 40% of SVT patients are diagnosed with an overt or latent MPN [1]. While the MPN-associated JAK2 V617F mutation is consistently reported in cohorts of SVT patients, several studies have investigated the role of CALR mutation analysis for MPN diagnosis in the presence of SVT with some debate existing [2-10]. Here, all reports published to date are summarized (Table 1). Briefly, of 944 patients studied only eight (0.8%) had evidence of a CALR mutation and of whom seven already had a previous diagnosis of an MPN.
Table 1 Summary of studies investigating CALR mutation status in splanchnic vein thrombosis
MPN patients with CALR mutations have a significantly lower overall risk of thrombosis than their counterparts harboring the JAK2 V617F and this is clearly the case with respect to SVT. While CALR mutated MPN patients may develop SVT, summarizing those published studies to date, routine investigation for these mutations appears not to be indicated in the diagnostic algorithm for SVT where no clinical or hematological features of an MPN are present.