This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Iron deficiency anemia, Subject name: Pathology
Ring sideroblast in myelodysplastic syndrome is associated with which gene mutation? 
Select and explain. 
A. ASXL1, B. EZH 2, C. TET 2, D. SF3B1
D: SF3B1
Answer: D: SF3B1 
Explanation: Myelodysplastic syndrome: Group of clonal stem cell disorders characterized by maturation defects, that are associated with ineffective hematopoiesis & have high risk of transformation to AML. - Myelodysplastic Syndrome with Ring Sideroblastic(MDS-RS) entity is earlier called as Refractory anemia with Ring Sideroblasts.(RA-RSS). - It is diagnosed: Only when >15% of early RBC are Ringed sideroblasts. Also if >5% of early RBC are RS and associated with mutation SF3B1. This mutation is a/w better prognosis.