1, 6, and 19
Msud is caused when a tightly clustered group of proteins [branched-chain ketoacid dehydrogenase] does not work properly.
This multienzyme complex has three subunits encoded by four different genes. Three of them - on chromosomes 1, 6, and 19, have been found to have mutations that can result in msud. The msud family support group (http://www.Msud-support.Org/) has more information.