Homocitrullinuria and homoargininuria in lysinuric protein intolerance

A 14-year-old boy with lysinuric protein intolerance had increased plasma and urinary concentrations of homocitrulline and homoarginine. The accumulation of carbamylphosphate due to depleted supply of ornithine for the urea cycle may be responsible for the enhanced synthesis of homocitrulline and homoarginine. A renal clearance study showed that the tubular transport of homoarginine in the patient was impaired. In lysinuric protein intolerance, membrane transport system for homoarginine may be defective because it is presumed that homoarginine shares a common transport system with the dibasic amino acids.