In this study we show that the proximal del(5q) candidate gene HSPA9 regulates erythroid maturation in human CD34+ cells, suggesting HSPA9/mortalin may be a potential target to treat anemia in del(5q) MDS patients by reactivating its expression from the residual wild-type nondeleted allele. This evidence concerns the gene HSPA9 and myelodysplastic syndrome.