In a cytogenetic and mutational study of 305 MDS with del(20q) whose samples were referred to the MLL Munich Leukemia laboratory, the most represented diagnostic category was RCUD (133 patients, 43.6%), among which 80.5% had del(20q) as sole abnormality.26 High-throughput sequencing can also help in the diagnosis of MDS in difficult cases by detecting mutations frequently associated with MDS, including TET-2, ASXL1, SF3B1, SRSF2, RUNX1 and DNMT3A.27,28 On the other hand isolated mutations of TET2, ASXL1 or DNMT3a can be found in elderly apparently healthy persons.29 Here, RUNX1 is linked to myelodysplastic syndrome.