USMLE

Systemic Primary Carnitine Deficiency

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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

Systemic primary carnitine deficiency is caused by a deficiency of carnitine, which is the compound responsible for the transport of fatty acids into the mitochondrial matrix. A lack of carnitine therefore leads to the build-up of fatty acids and fatty acyl-CoA, which can be toxic to cells. During periods of fasting, the body relies on hepatic glycogen stores for about the first 24 hours. After this, fat will be mobilized to the liver, where it will undergo beta-oxidation and subsequent conversion into ketone bodies. In patients with systemic primary carnitine deficiency however, the fat cannot be broken down, so ketone bodies cannot be formed. This leads to the finding of hypoketotic hypoglycemia, which is essentially just a hypoglycemic state that is NOT accompanied by ketogenesis. MCAD is a similar disease that hits a different step in this same pathway, so it may also present with hypoketotic hypoglycemia.