Methylmalonate semialdehyde dehydrogenase (MMSDH) deficiency is a rare autosomal recessive disorder with varied metabolite abnormalities, including accumulation of 3-hydroxyisobutyric, 3-hydroxypropionic, and methylmalonic acids, as well as beta-alanine. Reported clinical presentations vary from a mild or uneventful clinical course. Severe developmental delay may be present. Dysmorphic facial features and congenital brain dysgenesis with intracerebral calcifications have also been described. Mutations in the ALDH6A1 gene coding for MMSDH are associated with this disease.
