Definition: inherited genetic disorder characterized by the impaired break down of branched-chain amino acids (BCAA)

Epidemiology

Etiology

autosomal recessive

Pathophysiology

• Absent or deficient branched-chain alpha-ketoacid dehydrogenase → impaired degradation of BCAA (valine, leucine, isoleucine) → elevated α-ketoacid formation

Clinical features

• Symptom onset: early neonatal period
• Vomiting, lethargy, poor feeding
• Sweet-smelling urine (maple syrup or burnt sugar odor)
• Intellectual disability
• Dystonia
• Damage to the CNS can be severe (elevated leucine level leads to brain injury)
• Death may occur without appropriate treatment

Diagnostics

• Serum
  • Increased levels of alpha-ketoacids (especially leucine alpha-ketoacids)

Treatment

• Avoid foods containing BCAA
• Supplementation of thiamine, a cofactor of branched-chain alpha-ketoacid dehydrogenase