GTR Home > Conditions/Phenotypes > Maple syrup urine disease

Disease characteristics

Excerpted from the GeneReview: Maple Syrup Urine Disease
Maple syrup urine disease (MSUD) is classified as classic or intermediate. Twelve hours after birth, untreated neonates with classic MSUD have a maple syrup odor in cerumen; by 12-24 hours, elevated plasma concentrations of branched-chain amino acids (BCAAs) (leucine, isoleucine, and valine) and allo-isoleucine, as well as a generalized disturbance of plasma amino acid concentration ratios; by age two to three days, ketonuria, irritability, and poor feeding; by age four to five days, deepening encephalopathy manifesting as lethargy, intermittent apnea, opisthotonus, and stereotyped movements such as "fencing" and "bicycling." By age seven to ten days, coma and central respiratory failure may supervene. Individuals with intermediate MSUD have partial BCKAD enzyme deficiency that only manifests intermittently or responds to dietary thiamine therapy; these individuals can experience severe metabolic intoxication and encephalopathy during sufficient catabolic stress.

Associated genes

  • Also known as: BCKDE1A, MSU, MSUD1, OVD1A, BCKDHA
    Summary: branched chain keto acid dehydrogenase E1, alpha polypeptide

  • Also known as: RP1-279A18.1, E1B, dJ279A18.1, BCKDHB
    Summary: branched chain keto acid dehydrogenase E1, beta polypeptide

  • Also known as: RP11-305E17.3, BCATE2, BCKAD-E2, BCKADE2, E2, E2B, DBT
    Summary: dihydrolipoamide branched chain transacylase E2

Clinical features

  • Hypertonia
  • Intellectual disability
  • Lactic acidosis
  • Seizure
  • Pancreatitis
  • Hallucinations
  • Feeding difficulties in infancy
  • Vomiting
  • Ataxia
  • Muscular hypotonia
  • Lethargy
  • Coma
  • Growth abnormality
  • Hypoglycemia
  • Ketosis
  • Cerebral edema
  • Elevated plasma branched chain amino acids
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