CALR and myeloproliferative disorder: The Bcr/abl-negative MPN is a leading cause of SVT, accounting for 40% of BCS and 30% of extra-hepatic portal vein obstructions, while other MPN molecular markers, such as mutations in JAK2 exon 12, CALR, and MPL genes, are very rarely recognized as promoters of thrombotic events [20].