Homocitrullinuria and homoargininuria in hyperargininaemia

Summary A four‐year‐old boy with hyperargininaemia had increased urinary excretion of homocitrulline and homoarginine. A single oral lysine load created a marked increase in these amino acids in plasma. A daily oral lysine supplementation resulted in a remarkable urinary leakage of homocitrulline and homoarginine. These findings suggest that the patient had an enhanced synthesis of these amino acids.