Exam 2

Question 1

Urine odour and disorders

Answer 1

1. Maple Syrup Urine Disease (MSUD):
   
   • Urine Odor: Sweet, maple syrup-like odor
   • Urine Color: Light or clear
   • Enzyme Defect: Branched-chain alpha-keto acid dehydrogenase complex
2. Tyrosinemia:
   
   • Urine Odor: Cabbage-like or rancid butter odor
   • Urine Color: Dark, almost coffee-like
   • Enzyme Defect: Fumarylacetoacetate hydrolase
3. Trimethylaminuria (Fish Odor Syndrome):
   
   • Urine Odor: Fish-like odor
   • Urine Color: Normal
   • Enzyme Defect: Flavin-containing monooxygenase 3 (FMO3)
4. Homocystinuria:
   
   • Urine Odor: Boiled cabbage-like odor
   • Urine Color: Normal
   • Enzyme Defect: Cystathionine beta-synthase
5. Isovaleric Acidemia:
   
   • Urine Odor: Sweaty feet or isovaleric acid odor
   • Urine Color: Mild to light
   • Enzyme Defect: Isovaleryl-CoA dehydrogenase

Question 2

Phenylalanine and Tyrosine

Answer 2

1) Phenylketonuria- phenylalanine hydroxylase
Mousy odour due to phenylacetate.
Phenylpyruvate, phenylacetate & phenylactate & phenylacetyl glutamine.
5 types.
Type 1 classical Phenylketonuria-due to phenylalanine hydroxylase deficiency.
Type 2&3 due to defect in dihydrobiopeterin reductase.
Type 4&5 due to defect in dihydrobiopeterin biosynthesis.

Neurological manifestation due to decreased synthesis of dopamine, epinephrine and norepinephrine.

Hypopigmentation due to decreased melanin production causing light skin production and blue coloured eyes and fair hair.

Features are mental retardation, tremors, seizures , generalised hypopigmentation, light coloured hair and skin and mousy odour of urine.

Diagnosis test is Guthrie test and tandom mass spectrometry.

Alkaptonuria is due to deficiency of homogentisate oxidase causing accumulation of homogentisate.
Clinical features include dark coloured urine and dark staining of diaper in infancy, Skin , cartilage and sclera black or grey coloured, accumulation of alkaptons in tendons and bones, and arthrisis of large joints and intervertebral discs.

Tyrosinemia type 1 due to deficiency of fumaryl acetoacetate hydrolase giving odour to urine of cabbage like.

Tyrosinemia type 2 also called as richner henshart syndrome due to deficiency of tyrosine transaminase. Features include dermatitis and eye lesions.

Parkinson’s disease associated with decreased synthesis of dopamine. Clinical features include muscle rigidity, mask like face, tremors, lethargy and involuntary movement.It is treated by giving L-DOPA and carbidopa.

Question 3

Tryptophan metabolism

Answer 3

Products formed are Melatonin, Serotonin , NAD+,NADP+ …

Hartnups disease which is due to decreased absorption of tryptophan from intestine and renal tubules. 60mg of tryptophan forms 1mg of niacin. Symptoms are like pellagra are dermatitis, diarrhoea and dementia.

Carcinoid syndrome in which there is increased serotonin production causing skin flushing, facial skin lesions, diarrhea, rapid breathing and increased heart rate.

Xanthuurenate in urine due to PLP deficiency. Kynurinase is defective.

Question 4

Imbalance of water and dehydration and overhydration.

Answer 4

Dehydration - water output more than input with no loss of water.
Pure water depletion
In cases of coma and dysphagia
Pure salt depletion
Urinary loss of Na+ like in Addisons disease and in vomitting and diarrhea.
Combined water and salt depletion.
Results in sunken eyes, inelastic skin, low BP, decreased specific gravity, increased thirst and hallucinations.

Osmolarity
Specific gravity of urine
Thirst and dry pinched tongue
More ADH levels and secretion.