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

Alkaptonuria is an autosomal recessive disorder resulting from defects in the metabolism of tyrosine.

Specifically, alkaptonuria is caused by a deficiency of homogentisate oxidase, resulting in the accumulation of homogentisic acid. Homogentisic acid forms a pigment, and its buildup leads to ochronosis, or a bluish-black discoloration of sclera and connective tissue.

In addition, urine that turns black upon prolonged exposure to air is observed. Homogentisic acid is also toxic to cartilage, which can lead to a clinical presentation of joint pain and arthritis in patients.

Find Alkaptonuria and other Metabolic Disorders among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Shelf Exams.