Thus, on the assumption that some MDS cases with a normal karyotype might also have reduced expression of a gene or genes within the 20q CDR, we undertook an expression analysis of CD34+ cells from 18 MDS cases with a normal karyotype and the eight cases with a 20q aberration (Supplementary file 1A), compared to CD34+ cells from four normal bone marrow samples. The gene discussed is CD34; the disease is myelodysplastic syndrome.