Around 10%–25% of MDS patients harbor an interstitial heterozygous deletion on the long arm of chromosome 5 [del(5q)], creating haploinsufficiency for a large set of genes, including HSPA9. The HSPA9 gene encodes for the protein mortalin, a highly conserved heat shock protein predominantly localized in mitochondria. The gene discussed is HSPA9; the disease is myelodysplastic syndrome.