Disorders of Amino Acid Metabolism

Question 1

Oxoprolinuria

Answer 1

deficiency of 5 oxoprolinase enzyme

Question 2

Hyperammonemia

Answer 2

• Def. in any of enzymes of urea cycle
• Risk inc. if block is earlier as ammonia itself accumulates
  1. Respiratory alkalosis
  2. Encephalopathy
  3. Vomiting
  4. Irritability
  5. Lethargy
  6. MR

Question 3

Ornithine transporter deficiency

Answer 3

HHH
1. Hyperornithemia
2. Hyperammonemia
3. Homocitrullinuria
Ornithine accumulates in cytoplasm

Question 4

Ornithine transcarbamoylase deficiency

Answer 4

• X linked
  1. Hyperammonemia
  2. Aversion to high protein diet
  3. High glutamine levels in CSF and blood

Question 5

Argininosuccinate synthetase deficiency

Answer 5

1. Hyperammonemia
2. Citrullinemia
3. Citrullinuria
4. Elevated CSF citrulline levels

Question 6

Hepatic coma

Answer 6

Acquired hyperammonemia/ Portal systemic encephalopathy

• characteristic of liver failure
• toxins bypass liver and conc. in systemic circulation inc.
  1. Altered sensorium
  2. Convulsions
  3. Ascites
  4. Jaundice
  5. Hepatomegaly
  6. Edema

Question 7

A 6-month-old infant began to vomit occasionally and
ceased to gain weight. At 9 months of age he was readmitted to the hospital. Routine examination and laboratory analysis
were normal. After one week, he became drowsy, had fever,
pulse was elevated, and there was hepatomegaly. EEG
was done and was grossly abnormal. Blood ammonia was
elevated and urine contained high amount of glutamine
and uracil.

Answer 7

Hyperammonemia

OTC deficiency

Question 8

Nonketotic Hyperglycemia

Answer 8

• defect in glycine cleavage system
• Gly levels inc. in blood, urine, CSF
  1. Severe MR
  2. Seizures
  No effective management

Question 9

Primary hyperoxaluria

Answer 9

• autosomal recessive
• excess production and excretion of oxalates (600mg/day)
• protein targeting defect
• Alanine glyoxylate aminotransferase usually in peroxisomes. But here, in mitochondria
• it converts glyoxalic acid to gly
• so, inc. glyoxalate and oxalates produced
  1. Nephrolithiasis
  2. Renal colic
  3. Haematuria

Question 10

Cystinuria

Answer 10

• Garrod’s tetrad
• autosomal recessive
• deficiency in transport of AA
• Cyanide nitroprusside test +ve
  1. Abnormal excretion of cystine, arginine, lysine and ornithine
  2. Crystalluria, calculi formation
  3. Obstructive uropathy

Question 11

Cystinosis

Answer 11

• widespread deposition of Cys in lysosomes
• autosomal recessive
• due to abnormal transport of Cys

Question 12

Oasthouse syndrome

Answer 12

• malabsorption of methionine

- excrete Met, aromatic and branched AA

Question 13

Cystathione beta synthase def.

Answer 13

• inc. plasma and urine levels of Met and HomoCys
• +ve cyanide nitroprusside test
  1. MR
  2. Charlie chaplin gait
  2. Skeletal deformities
  4. Ectopic lentis, glaucoma
  5. Intravascular thrombosis

Question 14

N5 N10 Methylene THFA reductase deficiency

Answer 14

• reduced Met syn.
• inc. HomoCys in urine
  1. Behavioural changes
  2. Vascular abnormalities

Question 15

Cystathionuria

Answer 15

• Cystathione def.
• autosomal recessive
• -ve cyanide nitroprusside test
• Cystathione in urine
  1. MR
  2. Anaemia
  3. Thrombocytopenia
  4. Endocrinopathies

Question 16

A 36-year-old woman reported with a dull pain in the
left flank which was radiating towards left leg. She
reports fever and inability to pass urine for the last few
days. Similar history of illness was reported in the last 6
months. She was anemic and abdomen was tender. Routine
urinalysis revealed presence of RBC, pus cells, WBC
casts, characteristic hexagonal crystals and amino acids.

Answer 16

Cystinuria

Question 17

An adolescent girl presents with subluxation of lens and
mental retardation. On examination, she is tall and thin
with elongated limbs. Mild scoliosis was present with pectus excavatum and genu valgum.

Answer 17

Homocystinuria due to cystathione beta synthase deficiency