Urea Cycle Defects

Question 0

UCD Symptoms

Answer 0

Mild: sx during metabolic stress or chronic developmental delay
Moderate: FTT, developmental delay
Severe: poor feeding, lethargy, emesis, HYPERPNEA, hypotonia
hyperpnea can&raquo_space; respiratory alkalosis
*Arginase deficiency&raquo_space; SPASTIC DIPLEGIA

Question 1

UCD Pathophysiology

Answer 1

Can’t convert excess nitrogen into urea&raquo_space;
Excess ammonia, glutamine, gylcine

all AR except OTC Deficiency (x-linked, affects girls to varying degrees)

Question 2

UCD Diagnosis

Answer 2

Urine OA/Serum AA Patterns
CPS1 Defiency:
high ammonia, glutamine, glycine (plasma)
low citrulline (plasma)
normal orotic acid (urine)
OTC Deficiency:
high ammonia, glutamine, glycine (plasma)
high OROTIC ACID (urine)
low citrulline (plasma)
Citrullinemia: argininosuccinate synthetase deficiency
high citrulline (plasma and urine)
low argininosuccinate (plasma)
high ammonia, glutamine, ALANINE (plasma)
slightly high orotic acid (urine)
Arginase Deficiency: hyperammonemia

Question 3

UCD Treatment

Answer 3

Alternative methods of nitrogen excretion:
NaBenzoate, Phenylbutyrate
Protein restriction
HD for severe hyperammonemia during crisis