Medicine & USMLE

Maple Syrup Urine Disease

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Metabolic Disorders
  1. Albinism
  2. Pyruvate Dehydrogenase Deficiency
  3. Pyruvate Kinase Deficiency
  4. G6PD Deficiency
  5. Essential Fructosuria
  6. Hereditary Fructose Intolerance
  7. Galactosemia
  8. Galactokinase Deficiency
  9. Lactase Deficiency
  10. Ornithine Transcarbamylase Deficiency
  11. Phenylketonuria (PKU)
  12. Maple Syrup Urine Disease
  13. Alkaptonuria
  14. Homocystinuria
  15. Cystinuria
  16. Propionic Acidemia
  17. Lesch-Nyhan Syndrome
  18. Systemic Primary Carnitine Deficiency
  19. MCAD Deficiency

Maple Syrup Urine Disease (MSUD) is an autosomal recessive metabolic disorder that leads to the accumulation of branched-chain amino acids.

Maple Syrup Urine Disease is caused by a defect in branched-chain ketoacid dehydrogenase, a Vitamin B1 (Thiamine)-dependent enzyme, which leads to the accumulation of the branched-chain amino acids:isoleucine, leucine, and valine.

Infants affected have urine with a distinctive sweet odor that is reminiscent of maple syrup. Accumulation of branched-chain amino acids leads to a number of CNS problems: developmental delay, lethargy, and posturing (decorticate or decerebrate). If untreated, patients usually die in infancy.

Since thiamine pyrophosphate (TPP) is a cofactor for branched-chain ketoacid dehydrogenase, some forms of maple syrup urine disease may improve and be treated with thiamine.

Find Maple Syrup Urine Disease and other Metabolic Disorders among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Exams.