Long-term survival of patients with argininosuccinate synthetase deficiency.

OBJECTIVE: To monitor long-term survival and outcome of patients with neonatal-onset argininosuccinate synthetase deficiency (ASD) who were treated with specific therapeutic protocols designed to activate alternative pathways of waste nitrogen excretion. DESIGN: Patients for this study included 24 infants born before 1990 and rescued from hyperammonemic coma caused by neonatal-onset ASD; they were referred to this center for enrollment in ongoing clinical studies of sodium benzoate, sodium phenylacetate, and sodium phenylbutyrate. Collaborating physicians throughout the United States and Canada provided information on survival, intellectual development, intercurrent hyperammonemic episodes, and anthropometric and biochemical measurements. RESULTS: The cumulative survival rate was 87.5% at 5 years and 72% at 10 years of age. Survivors include 15 patients currently treated with high doses of sodium phenylbutyrate; two patients have withdrawn. Among the treated group, 11 are classified as severely to profoundly mentally retarded. The remaining four patients have IQ measurements in the borderline to mentally retarded range. All patients have had intercurrent hyperammonemic episodes; our data indicate that the frequency of the episodes has decreased with implementation of the current protocol. These patients are growth retarded, but most have height-for-weight z scores within 2 SD of the mean. Laboratory studies of plasma amino acids and of hematopoietic, renal, and hepatic function are within normal limits with the exception of slightly elevated serum aminotransferase values. CONCLUSION: Our results indicate that these drugs are safe and that the current protocol improves survival rates. However, survival is accompanied by mental retardation, growth retardation, risk of hyperammonemic episodes, and the necessity of lifetime adherence to strict medication and dietary management.

Citrulinemia / Citrulinemia

Se describen los casos clínicos de tres pacientes con citrulinemia, que fue diagnosticada respectivamente a las edades de tres meses, siete días y siete meses. En todos la concentración sanguínea de amonio era anormalmente alta (>200ug por ciento) y las de citrulina en suero fueron de 353, 1.759, 289 nm/ml respectivamente. El tratamiento consistió en una dieta hipoproteica e hipercalórica, con suplementos de L-carnitina (100 mg x kg x día). L-arginina (70 a 120 mg x kg x día) y vitaminas. Las manifestaciones clínicas de la enfermedad son mas severas y precoces cuanto menor es la actividad residual de la rginina succínico sintetasa, cuya deficiencia es responsable del trastorno y que está practicamente ausente en la forma neonatal

Prospective management of a child with neonatal citrullinemia.

A patient with neonatal citrullinemia caused by severe deficiency of argininosuccinate synthetase was treated prospectively according to the currently accepted protocol. We gradually reduced the doses and then discontinued treatment with sodium benzoate and phenylacetate; blood glutamine levels were maintained in the normal range, but ammonia was mildly elevated. Growth and development progressed normally through 31 months of age. Some patients with citrullinemia can be successfully managed without daily sodium benzoate and phenylacetate therapy.

Prospective treatment of urea cycle disorders.

We present a diagnostic and therapeutic protocol designed to prevent clinical expression of inborn errors of urea synthesis in the neonatal period, and discuss the long-term developmental outcome of survivors. The families of 32 infants, among 43 identified prenatally as being at risk for a urea cycle disorder, chose to have their infants treated according to a diagnostic and therapeutic protocol, beginning at birth. The therapy was effective in avoiding neonatal hyperammonemic coma and death in seven patients with carbamoyl phosphate synthetase deficiency, argininosuccinate synthetase deficiency, and argininosuccinate lyase deficiency. When treated prospectively, five of eight patients with ornithine transcarbamylase deficiency avoided severe hyperammonemia and survived the neonatal period. Two patients with carbamoyl phosphate synthetase deficiency and two with ornithine transcarbamylase deficiency have subsequently died; three additional patients with the latter disorder have received orthotopic liver transplants. Our experience suggests that these surviving patients have had a more favorable neurologic outcome than patients rescued from neonatal hyperammonemic coma. However, all of them require a burdensome medical regimen and may have handicaps that include impairment of development and recurrent episodes of hyperammonemia. Further, those with deficiency of carbamoyl phosphate synthetase or ornithine transcarbamylase have a high mortality rate.

Differentiation of transient hyperammonemia of the newborn and urea cycle enzyme defects by clinical presentation.

We reviewed clinical data in 33 patients with transient hyperammonemia of the newborn (THAN): six previously unreported cases and 27 from the literature. Thirteen neonates with urea cycle enzyme deficiencies (UCED) served for comparison. No differences were found in the incidence of perinatal complications, route of delivery, Apgar scores, sex, or incidence or time of onset of seizures. On the other hand, neonates with THAN had significantly lower birth weights (mean +/- SEM 2282 +/- 78 gm vs 3336 +/- 222 gm, P less than 0.001) and gestational ages (35.1 +/- 0.5 weeks vs 39.6 +/- 0.5 weeks, P less than 0.001). Mean time of onset of respiratory distress (3.9 +/- 1.4 hours vs 71.5 +/- 26.1 hours, P less than 0.001), ventilatory support (P less than 0.001), lethargy (P less than 0.005), and coma (P less than 0.005) occurred earlier in THAN. Distinctive laboratory findings in patients with THAN included abnormal chest radiographic findings and plasma ammonium concentrations that were higher (1871 +/- 209 microM vs 973 +/- 169 microM, P less than 0.02) at an earlier age. Respiratory distress occurred in all but one patient with THAN before 24 hours; in contrast, only 62% of infants with UCED had respiratory symptoms, and none before 30 hours. In this retrospective study, the clinical presentation alone differentiated THAN from UCED.

Neonatal citrllinemia: treatment with keto-analogues of essential amino acids.

A patient with neonatal onset citrullinemia survived to 8 months of age when treated with a mixture of essential amino acids and their keto-analogues. The initial plasma citrulline concentration was 2.7 mM; the blood ammonia concentration was greater than 500 muM. During the first week of therapy, the blood ammonia concentration became normal and that of plasma citrulline was reduced by almost 50%. It was possible to institute progressive increases in dietary calories and protein; growth and developmetn with resolution of almost all clinical signs of disease ensued. The patient died at 8 months of age after an episode of diarrhea and dehydration, probably of viral origin.