Tyrosinemia Enzymes : Mnemonic

Mnemonic: FAHeem TATtooes because of Histrionic Personality Disorder (HPD)

Tyrosine is necessary for biosynthesis of catecholamines, thyroid hormones and melanin pigment.

1. Tyrosinemia type I (Tyrosinosis/Hepatorenal tyrosinemia):

• Enzyme defect: FAH (Fumaryl-acetoacetate hydroxylase)
• Last enzyme in the cycle
• Cabbage like odor
• Hepatocellular carcinoma
• Renal tubular acidosis
• Peripheral neuropathy

2. Tyrosinemia type II (Oculo-cutaneous/Richner-Hanhart):

• Enzyme defect: TAT (Tyrosine Amido-Transferase)
• 1st enzyme in the cycle (hepatic enzyme)
• Corneal erosions
• Palmoplantar keratosis
• Mental retardation

3. Tyrosinemia type III (Neonatal):

• Enzyme defect: HPD (Hydroxy-Phenylpyruvate-Dioxygenase)
• Second enzyme in the cycle
• Neurologic dysfunction

BONUS

Alkaptonuria: Mnemonic – HAO

• Enzyme defect: HAO (Homogentisic Acid Oxidase)
• Clinical features:
  • Homogentisic aciduria (urine turns black on standing; Benedict’s/FeCl3 test positive)
  • Arthritis (large joints; narrowing of joint space and calcification of IV disc)
  • Ochronosis (darkening of sclera, ear and nose cartilage, tympanic membrane, palmoplantar skin, large joints and IV disc due to deposition of benzoquinone acetate, i.e. oxidized homogentisic acid)