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This study reports a case of citrullinemia in an infant, successfully managed with dietary protein restriction and amino acid therapy. The infant shows normal development, suggesting effective treatment for this urea cycle disorder.
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Citrullinemia is a rare urea cycle disorder characterized by elevated plasma citrulline levels.
- Early diagnosis and intervention are crucial for managing hyperammonemia and preventing neurological damage.
Observation:
- An 18-month-old female infant diagnosed with citrullinemia at 5 days of age presented with markedly elevated plasma and urine citrulline.
- Hyperammonemia was observed at 1 month of age, with serum ammonia levels rising significantly.
- Argininosuccinic acid synthetase activity in skin fibroblasts was measured to assess enzyme function.
Findings:
- Dietary protein restriction (1.6 gm/kg/day) and temporary L-amino acid supplementation normalized serum ammonia levels.
- The infant exhibited normal physical and mental development by 18 months of age.
- Family screening suggested potential genetic heterogeneity contributing to phenotypic variation in citrullinemia.
Implications:
- This case highlights the effectiveness of early dietary management in achieving favorable outcomes for citrullinemia.
- Understanding genetic heterogeneity is important for predicting disease course and tailoring treatment strategies.
- Further research into the genetic basis of citrullinemia can improve diagnostic and therapeutic approaches.
Abstract:
An 18-month-old female infant was found to have citrullinemia on routine plasma screening by the Scriver Method at 5 days of age. At 10 days of age, plasma citrulline concentration was 0.704mumol/ml (normal, 0.010 to 0.030mumol/ml) and has remained 60 to 80 times higher than normal. Urine citrulline concentration was markedly elevated. Hyperammonemia occurred at 1 month of age. The serum ammonia concentration was 473mug/100 ml (normal, 50 to 250 mug/100 ml) and rose to 770mug/100 ml at 4 months of age. Dietary protein was restricted to 1.6 gm/kg/day. Without further change in protein intake, the serum ammonia concentration decreased to 280mug/100 ml and, since then, it has returned to normal. The addition of three synthetic L-amino acids was required for a short time during dietary therapy. At 10 months of age, the infant was given a normal diet. At 18 months of age, her physical and mental development is normal. Activity of argininosuccinic acid synthetase measured in skin fibroblasts was 0.0037mumol of radioactive carbon dioxide per milligram of protein per hour. To demonstrate heterozygosity, fasting plasma citrulline concentrations were measured in five members of the family. Comparison of findings in this patient with those reported in the literature suggests phenotypical variation of the disease, probably due to genetic heterogeneity.