Tyrosinemia Enzymes : Mnemonics

Tyrosinemia is an important topic for USMLE, NEET and medical school exams.
Let’s learn tyrosinemia mnemonics in this high-yield article.

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Tyrosinemia   Inborn error in the degradation of the tyrosine.    People have problems breaking down an amino    acid tyr...

 Tyrosinemia type I (Tyrosinosis/Hepatorenal tyrosinemia):

Type I Tyrosinemia Tyrosinemia 1 occurs when an enzyme,  called fumarylacetoacetase (FAH), is either  missing or not work...

Symptoms of Type I Tyrosinemia   Failure to gain weight or grow   Diarrhea, bloody stools and vomiting   Jaundice of sk...
  • 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):

Type III Tyrosinemia Deficiency of 4-hydroxyphenylpyruvate  dioxygenase (HPPD) Caused by a mutation in the HPPD gene  th...
Symptoms of Type IIITyrosinemia Mild mental retardation Seizures Loss of balance and coordination  (intermittent ataxia...
  • 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
Goals of dietary management:1.   Support an appropriate rate of growth2.   Support normal intellectual     development3.  ...
The following treatments are often recommendedfor children with tyrosinemia 1:2.   A medication called nitisinone (Orfadin...


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)

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