Abstract
Scott-Emuakpor et al. (6) described a case of citrullinemia in a 33-year-old man who also had raised plasma and urine levels of lysine, homocitrulline, and homoarginine. It was therefore postulated that the patient was synthesizing urea by a late developing cycle whose intermediates were the homo-analogues of the ordinary urea cycle. We have also observed similar raised levels of these amino acids in a child with the same defect of argininosuccinic acid synthetase who died at 7 months of age [4, 8].
However, normal levels of lysine and homocitrulline were found in all the patients in nine families with disorders of the urea cycle other than citrullinemia which we have investigated. Furthermore, homoarginine could not be detected in two of the patients with hyperammonemia and four of the patients with argininosuccinic aciduria whose plasma and urine were examined for this amino acid [5]. From all of these findings it was concluded [5] that the high levels of lysine, homocitrulline, and homoarginine in citrullinemia do not necessarily indicate an alternative pathway of urea formation.
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Levin, B., Oberholzer, V. & Palmer, T. Citrullinemia and an Alternative Urea Cycle: Letter to the Editor. Pediatr Res 7, 728 (1973). https://doi.org/10.1203/00006450-197308000-00010
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DOI: https://doi.org/10.1203/00006450-197308000-00010
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