A pediatric patient with classical citrullinemia who underwent living-related partial liver transplantation.

Patients with inborn errors of metabolism undergo liver transplantation, but the effect of transplanting the liver of healthy carriers of these conditions has not been fully clarified. A 6-year-old girl with classical citrullinemia, who repeatedly suffered from hyperammonemia, underwent living-related liver transplantation by using a segment of the liver of her mother, who was a heterozygote carrier for classical citrullinemia. Hyperammonemia alleviated in the patient after the transplantation, thereby dramatically improving her quality of life. Although the levels of plasma and urinary citrulline remained high postoperatively, there was no marked difference in the level of plasma citrulline up to 1 month after surgery when compared with that of previously reported orthotopic liver transplantation cases with classical citrullinemia.

Plasma concentrations and renal clearance of orotic acid in argininosuccinic acid synthetase deficiency.

Argininosuccinic acid synthetase deficiency (ASD) is a rare disorder of urea cycle metabolism, with pronounced citrullinemia and orotic aciduria being characteristic biochemical features. To further investigate the role of plasma orotic acid and its possible use for monitoring the metabolic status in ASD, we determined plasma orotic acid, amino acid, and ammonium levels in plasma samples collected over a period of 3 years from a patient who is now 8 years of age. Orotic acid plasma concentrations varied widely from less than 1 micromol/l to more than 60 micromol/l. The renal clearance of orotic acid was eightfold the glomerular filtration rate, thus supporting an active mechanism underlying the excretion of this pyrimidine. Data obtained during a metabolic crisis yielded a statistically significant linear correlation of orotic acid plasma levels with those of glutamine and ammonium, which are generally accepted for assessment of the successful treatment of this disorder. Our data revealed no advantage of plasma orotic acid concentrations over the established amino acids (glutamine and arginine) and ammonium for determining acute treatment responses. Since several effects of high levels of orotic acid have been described in mammals, further research is necessary to assess a possible contribution of orotic acid to the pathogenesis of ASD and the use of plasma orotic acid levels in the long-term monitoring of these patients.