Although maple syrup urine disease (MSUD) is rare with an incidence of 1 in 197,714 live births in the general population based on NBS data, among North American Old Order Mennonites, severe (”classic”) MSUD affects as many as 1 in 400 births due to a founder variant of BCKDHA (c.1312T>A, p.Tyr438Asn) [46,47]. This evidence concerns the gene BCKDHA and maple syrup urine disease.