Urea Cycle Disorders

Question 1

What is the function of the urea cycle?

Answer 1

To dispose of toxic ammonia created by deamination of amino acids.
Converts toxic ammonia to nontoxic urea for renal excretion

Question 2

True or false: metabolic acidosis is a common finding in those with urea cycle disorders

Answer 2

False: not prominent finding typically, can have a mild metabolic acidosis if ill secondary to dehydration and shock

Question 3

What symptoms would a neonate with severe urea cycle d/o present with?

Answer 3

Sx AFTER the first 24hrs of life;

1. Irritable
2. Vomiting
3. Lethargy
4. Seizures
5. Resp distress (resp alkalosis to compensate for NH4 Acidosis)
6. Coma

Question 4

What type of urea cycle defect typically presents in the neonatal period with severe sx?

Answer 4

Ornithine Transcarbamylase deficiency in boys (X-linked d/o)

Question 5

What types of symptoms do children with urea cycle disorders typically present with?

Answer 5

Hyperactive behavior and a refusal to eat high protein foods.

Question 6

What types of symptoms do adults with urea cycle disorders typically present with?

Answer 6

Typically if adult onset its a less severe deficiency. Can present with stroke like symptoms, lethargy, delirium

Question 7

What are children with urea cycle disorders at risk for when they are sick, or if they have poor intake?

Answer 7

Hyperammonemic crisis with catabolism or excessive protein intake

Question 8

How do you tx a child with urea cycle disorder acutely?

Answer 8

1. IV D10 (promote anabolic state)

2. Lipid emulsion infusion to provide protein-free energy

Question 9

How do you tx a child with urea cycle disorder long term?

Answer 9

1. Dietary protein restriction
2. Arginine/citrulline supplementation
3. Sodium or glycerol phenylbutyrate
4. Discuss sick day management plan
5. Liver transplant reduces recurrent episodes

Question 10

How is Ornithine transcarbamylase deficiency inherited?

Answer 10

X-linked

Question 11

OTC deficiency is X-linked, however, what is unique about ornithine transcarbamylase deficiency in girls?

Answer 11

Female carriers can also have severe disease

Question 12

What do plasma amino acids show in OTC deficiency?

Answer 12

Elevated glutamine (storage form of ammonium), decreased citruline, and arginine

Question 13

What does urine organic acid analysis show in ornithine transcarbamylase deficiency show?

Answer 13

High orotic acid

Question 14

How else can you test for OTC deficiency?

Answer 14

DNA testing