Aberrant DNA hypermethylation was detected much more frequently than chromosome aberrations. (A) Proportion of patients with chromosome aberrations detected by standard metaphase karyotyping or SNP-A by patient group. (B) Idiogram representing the chromosomal localization of concordantly hypermethylated loci (loci hypermethylated in more than 50% of patients with low-risk MDS and RAEB/AML). Chromosomes are numbered at the top. Gene names are indicated beside each hypermethylated locus. Genes marked with a box are hypermethylated in both low-risk MDS and AML/RAEB. Genes shown more than once represent those with more than one hypermethylated locus. (C) On a chromosome by chromosome basis, the proportion of patients with aberrant methylation detected on that chromosome was higher than the proportion of patients with a chromosome aberration involving that chromosome.