Urea Cycle Disorders

Question 1

OTC Deficiency

Ornithine Transcarbamylase

Answer 1

X-LINKED!
Most common
Plasma ammonia >150 umol/L with a normal anion gap and normal glucose
Low citrulline, high glutamine
Elevated orotic acid

Question 2

CPS1 Deficiency

Carbomylphosphate Synthetase I

Answer 2

Plasma ammonia >150 umol/L with a normal anion gap and normal glucose
Mutation on molecular analysis

Question 3

Citrullinemia Type I/ASS1 Deficiency

Answer 3

Argininosuccinate Synthetase I
Plasma ammonia >150 umol/L with a normal anion gap and normal glucose
 Mutation on molecular analysis
 High citrulline

Question 4

Argininosuccinic Aciduria/ASL Deficiency Argininosuccinate Lyase

Answer 4

In addition to hyperammonemia, has also have
chronic hepatomegaly and trichorrhexis nodosa (node like appearance of fragile hair)
Plasma ammonia >150 umol/L with a normal anion gap and normal glucose
 Mutation on molecular analysis
 High citrulline
 Enlarged hepatocytes on biopsy, which
may progress to fibrosis
 May have AST/AL T elevations

Question 5

NAGS Deficiency

N-acetyl glutamate synthase

Answer 5

Enzyme that yields cofactor for CPS1
Plasma ammonia >150 umol/L with normal anion gap and normal glucose
 Mutation on molecular analysis

Question 6

ARG Deficiency

Arginase

Answer 6

Symptoms of hyperammonemia are  triggered by stress/illness
Plasma ammonia >150 umol/L with normal anion gap and normal glucose Mutation on molecular analysis
High arginine

Question 7

ORT-1 Deficiency
Ornithine translocase (transporter)

Answer 7

Symptoms of hyperammonemia are  triggered by stress/illness

Plasma ammonia >150 umol/L with normal anion gap and normal glucose Mutation on molecular analysis

Question 8

Citrin Deficiency

Answer 8

Symptoms of hyperammonemia are  triggered by stress/illness

Plasma ammonia >150 umol/L with normal anion gap and normal glucose Mutation on molecular analysis