We unraveled the methylome architecture of the CCDC163P/MMACHC CpG island (CpG:33) and the TESK2 CpG island (CpG:51) by studying the epigenome-wide DNA methylation profile of the 17 epi-cblC cases [2, 3]. This evidence concerns the gene MMACHC and methylmalonic aciduria and homocystinuria type cblC.