Introduction to Maple Syrup Urine Deficiency

Maple Syrup Urine Disease gets its name from the distinctive sweet odor of affected infants’ urine. This condition is characterized by poor feeding, vomiting, lethargy and development delay during early infancy. If it is left untreated, MSUD can lead to seizures, coma and even death.

To go in depth, it is an inherited autosomal recessive disorder in which it is caused by the mutation in four specific genes, known as Branched Chain Keto-Acid Dehydrogenase E1 Alpha Polypeptide (BCKDHA), Branched Chain Keto Acid Dehydrogenase E1 beta polypeptide (BCKDHB), Dihydrolipoamide Branched Chain Transacylase E2 (DBT) and Dihydrolipoamide Dehydrogenase (DLD). These four genes encodes the components of the branched-chain alpha-keto acid dehydrogenase (BCKAD) complex, which catalyzes the catabolism of the branched-chain amino acids (BCAAs), known as Leucine, Isoleucine and Valine.

The mutations in these 4 genes will reduce or eradicates the functionality of BCKAD complex and thus preventing the catabolism of the 3 proteins. As a result, accumulation of these three amino acids and their corresponding keto acids will lead to encephalopathy (degenerative brain damage), causing mental retardation, neurological difficulties in walking and speech, seizures, or death.


Reference : 

http://ghr.nlm.nih.gov/condition/maple-syrup-urine-disease
http://learn.genetics.utah.edu/content/disorders/whataregd/msud/

http://www.health.state.mn.us/divs/fh/mcshn/ncfu/cond/msud.htm