Medicine & USMLE


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


Homocystinuria is an autosomal recessive disorder that is caused by an overaccumulation of homocysteine in the body. It’s caused by defects in cystathionine synthase, methionine synthase, vitamin B6, and MTHFR. Clinical manifestations of homocystinuria include marfanoid habitus and kyphosis, caused by defects in collagen cross-linking; ocular abnormalities such as lens subluxation; developmental delay; thrombosis and atherosclerosis; and finally hypopigmented skin and hair.