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Clinical and biochemical studies on periodic hyperammonemia with hyperlysinemia and homocitrullinuria
Insights
This study identifies a metabolic error linked to the lysine-urea cycle in an 18-year-old boy with recurrent hyperammonemia and neurological symptoms. L-lysine loading revealed reduced arginase activity, indicating a potential urea cycle disorder.
Area of Science:
- Biochemistry
- Genetics
- Pediatric Neurology
Background:
- The urea cycle is crucial for ammonia detoxification.
- Lysine metabolism is interconnected with the urea cycle.
- Disorders in urea cycle enzymes can lead to hyperammonemia.
Observation:
- An 18-year-old male presented with anorexia, vomiting, coma, and convulsions, worsening with age.
- Periodic hyperammonemia, hyperlysinemia, and homocitrullinuria were observed.
- Blood cell arginase activity was reduced following L-lysine oral loading.
Findings:
- L-lysine loading exacerbated hyperammonemia, leading to hyperlysinemia, hyperargininemia, hypercitrullinemia, and homocitrullinuria.
- The patient exhibited significantly reduced blood cell arginase activity.
- These findings suggest a metabolic error related to lysine metabolism and the urea cycle.
Implications:
- This case highlights a potential novel urea cycle disorder or a related metabolic anomaly.
- Understanding the interplay between lysine and urea cycle enzymes is critical for diagnosis.
- Further research into lysine-induced metabolic disturbances is warranted for effective therapeutic strategies.
Abstract:
An 18-year-old mentally and physically retarded boy, suffering from episodes of anorexia, vomiting, coma and convulsion which have been severer with advance in age, had periodic hyperammonemia, hyperlysinemia and homocitrullinuria. Blood cell arginase activity of the patient on normal diet was markedly reduced after an oral load of L-lysine. The oral loading tests of L-lysine revealed hyperammonemia, hyperlysinemia, hyperargininemia, hypercitrullinemia and homocitrullinuria. Etiology of metabolic error of our patient was discussed in reference to lysine-urea cycle.