SF3B1 and Thrombocytosis: Splicing factor 3b, subunit 1 (SF3B1). About 20% of patients with MDS and 60%–82% of patients with MDS with ringed sideroblasts (RS) and MDS/myeloproliferative neoplasms with RS and thrombocytosis harbor mutations in the splicing factor 3b, subunit 1 (SF3B1) [107,108,109].