Is RARS-T a new disease entity or a subtype of RARS or ET?

which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Is RARS-T a new disease entity or a subtype of RARS or ET? TO THE EDITOR: A recent report of " JAK2 V617F mutation in myelodysplastic syndrome, myelodysplastic syndrome/myelo-proliferative neoplasm, unclassifiable, refractory anemia with ring sideroblasts with thrombocytosis, and acute myeloid leuke-mia " by Jekarl DW et al. [1] has shown one patient with JAK2 V617F mutation among 7 patients with RARS-T. This 14.3% of JAK2 mutation rate seems to be lower than 58% of previously reported data in the review of Wardrop D and Steenma DP [2]. Fifty-four patients had JAK2 mutation among 93 patients with RARS-T in 10 serial studies. Additionally 2 of 27 JAK2 wild-type patients showed MPL W515 mutation. MPL W515 mutation is found in 5% of primary myelofibrosis and 1% of essential thrombocythemia (ET) cases [3]. But Jekarl DW et al did not report about this second mutation in their article. One more concern for this report was the incidence and the diagnosis of RARS-T. Seven patients were enrolled in this single-center study only for 3 years. Seven RARS-T patients seemed to be extraordinarily many, even when authors used WHO 2008 criteria which alleviates the criterion of thrombocy-tosis from 600,000/μL to 450,000/μL, and their center is one of the large tertiary hospitals in Korea. Also, there was no data on 7 RARS-T patients about the percentages of ring sideroblast (RS), and comorbidities which are necessary for the exclusion of other reacitve thrombocytoses such as inflammation or bleeding. The role of RS in the pathophysiology of RARS, RARS-T and RCMD-RS (this entity is recently combined with RCMD in WHO 2008 criteria) is not clearly elucidated now. Also the cutoff value of 15% is thought to be arbitrary. Seventy-three MDS patients with RS showed the wide range of RS between 1% and 86% [4]. The survival of patients with RARS-T was similar to that of patients with ET but better than that of patients with RARS [5]. The thrombohe-morrhagic complications of patients with RARS-T had not been reported except in some case repots. The recommended approach to RARS-T is same as in ET although anemia and neutropenia could be aggravated by cytoreductive therapy. Therefore, RARS-T, a provisional and new entity in WHO 2001 and 2008 criteria should be reconsidered whether it will be kept its own entity or be …