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)