Citrullinemia

What this deck covers

Citrullinemia in fourteen clinical teaching cases with worked explanations. Each case gives you a clinical vignette, four options, the correct answer, and an explanation of why each of the other three is wrong.

Diagnoses and management options tested

Across the fourteen cases you are asked to choose between options such as: Citrullinemia Type I (Classic), Neonatal bacterial sepsis, Organic acidemia (methylmalonic acidemia), Neonatal hepatitis with acute liver failure, Carbamoyl phosphate synthetase I (CPS1), Ornithine transcarbamylase (OTC), Argininosuccinate synthetase 1 (ASS1), Argininosuccinate lyase (ASL), Phenylalanine 1200 µmol/L elevated, tyrosine normal, Ornithine 450 µmol/L elevated, homocitrulline present, Methionine 850 µmol/L elevated, succinylacetone present, Phenylalanine >120 µmol/L with elevated Phe/Tyr ratio, Methionine elevated with positive succinylacetone, Excessive exercise-induced muscle hypertrophy, Oral lactulose and dietary protein restriction alone, IV acyclovir and broad-spectrum antibiotics empirically, Citrullinemia Type I with late-onset presentation, OTC deficiency, late-onset, Blocks hepatic amino acid deamination directly, Stimulates residual ASS1 enzyme activity, Chelates ammonia in the gut lumen, Facial dysmorphism, hepatosplenomegaly, skeletal dysplasia, Blistering skin lesions, alopecia, lactic acidosis, Cherry-red spot, coarse facial features, corneal clouding, Ornithine transcarbamylase (OTC) deficiency, Carbamoyl phosphate synthetase I (CPS1) deficiency.

Clinical pearls from this deck

• Severe hyperammonemia with NO acidosis and NO ketosis after a symptom-free interval following the first protein feeds = urea cycle disorder, and here citrullinemia type I. Ammonia rises rapidly >500 µmol/L causing hypotonia, absent reflexes, and a bulging fontanelle (cerebral edema). Plasma citrulline is dramatically raised (800–5000 µmol/L). Sepsis and organic acidemias both cause acidosis — absent here.
• ASS1 normally combines citrulline + aspartate → argininosuccinate (step 3). Block it and citrulline accumulates massively while NO argininosuccinate is made — the exact pattern here. Contrast: CPS1 → citrulline very LOW, orotic acid normal; OTC (X-linked) → citrulline low with HIGH urine orotic acid; ASL → citrulline only moderately up with argininosuccinate markedly ELEVATED.

The fourteen worked cases in this deck, with the images and the full explanation of every option, are part of Pediatric Case Review membership. See what is included.

More from this system: all metabolic and genetic decks and question sets · pediatric reference values.