Therefore, to gain insight into the molecular mechanisms underlying neurological deficits in IEM patients, we analyzed in peripheral whole blood the mRNA expression of a group of genes involved in brain development and synaptic function (ADORA2A, CACNA2D2, FMR1, IRAK1, LIN28A, PTEN, MECP2 E1/E2, THBS1, THBS3) in a cohort patients affected by UCD, MSUD and BCKDK deficiency. Here, MECP2 is linked to maple syrup urine disease.