Inborn Errors of Metabolism

Question 1

GNR sepsis (especially by E. coli) is associated with which metabolic disorder?

Answer 1

Galactosemia

Question 2

Name the IEM category: hypoglycemia, hyperammonemia, ketoacidosis, lactic acidosis, thrombocytopenia, granulocytopenia

Answer 2

Organic acidemias (all labs are ABNORMAL)

Question 3

Name the IEM category: elevated ammonia level to >100s with hypotonia, otherwise all other labs are NORMAL.

Answer 3

Urea cycle defect

Question 4

Name the IEM category: hyperammonemia, lactic acidosis, hypoglycemia, no ketoacidosis

Answer 4

Fatty Acid Metabolism Disorders (cannot produce ketoacids because issue with breaking down fats)

Question 5

Elevated pyruvate and lactic acid; also has elevated ammonia

Answer 5

Mitochondrial disorders (problems with aerobic respiration, so rely on anaerobic respiration); elevated ammonia because of increased muscle breakdown

Question 6

Amino acidopathy that acts like an organic acidemia?

Answer 6

Maple syrup urine disease (hypoglycemia, hyperammonemia, acidosis)– progressive neuropathy and seizures. Present at birth.

Question 7

Name the disorder: GALT deficiency.

Answer 7

Galactossemia (galactose-1-P UDT deficiency)

Question 8

What is the most common mode of inheritance for most inborn errors of metabolism? Which two disorders are exceptions?

Answer 8

Autosomal recessive.

Hunter’s Syndrome and Ornithine Transcarbamoylase (both of them are X-linked recessive).

Question 9

Describe isovaleric acidemia and treatment.

Answer 9

Smelly feet smell. 
Seizures. 
Decreased appetite/poor feeding.
Prone to infections.
NO lactic acidosis.
Diagnose-- urine organic acids
Treatment-- stop protein intake and maintain low protein intake. High L-carnitine (helps mobilize more fatty acids for energy), hydration.

“ERIC” has smelly feet.

Question 10

Describe glutaric acidemia.

Answer 10

Smelly feet smell.
Diagnose– urine organic acids
Treatment– stop protein intake, high L-carnitine, hydration

“ERIC has smelly feet”

Question 11

Describe methylmalonic acidemia.

Answer 11

Hypoglycemia, hyperammonemia, lactic acidosis, ketoacidosis.
Hypotonia, seizures, poor feeding, vomiting.
Diagnose with urine organic acids, treat with vitamin b12.

Question 12

Describe propionic acidemia.

Answer 12

All labs are abnormal.
Same as methylmalonic acidemia (poor feeding, seizures, hypotonia).
Diagnose with urine organic acids, treat with vitamin B7 or biotin.

Question 13

How do you diagnose a urea cycle defect?

Answer 13

Urine orotic acid, measure serum amino acid levels (citrulline, arginine, arginosuccinate), low BUN (cannot produce urea from ammonia)

Question 14

Order of urea cycle metabolites?

Answer 14

Carbamyl phosphate + ornithine –> Citrulline –> Argininosuccinate–> arginine

Question 15

Name the diagnosis: elevated urine orotic acid, low citrulline; error is at which enzyme?

Answer 15

Ornithine transcarbamylase deficiency

Question 16

Elevated citrulline, low argininosuccinate; error is at which enzyme?

Answer 16

Citrullinemia secondary to argininosuccinate synthetase deficiency

Question 17

Elevated argininosuccinate, low arginine; error is at which enzyme?

Answer 17

Argininosuccinic acidemia secondary to argininosuccinate lyase deficiency