Neonatal argininosuccinic aciduria-survival after early diagnosis and dietary management

Nutritional therapy improves growth and protein status of children with a urea cycle enzyme defect

BACKGROUND

Poor growth has been described in patients with urea cycle enzyme defects treated with protein-restricted diets, while protein status is seldom reported.

OBJECTIVE

To assess the effects of nutritional therapy with a medical food on growth and protein status of patients with a urea cycle enzyme defect.

METHODS

A 6-mo multicenter outpatient study was conducted with infants and toddlers managed by nutrition therapy with Cyclinex-1 Amino Acid-Modified Medical Food with Iron (Ross Products Division, Abbott Laboratories, Columbus, OH). Main outcome variables were anthropometrics and plasma amino acids (selected), albumin, and transthyretin concentrations.

RESULTS

Seventeen patients completed the study. Mean (+/-SE) baseline age was 11.30+/-3.20 months (median 4.40 months; range 0.22-38.84 months). Length and weight z-scores increased significantly during the 6-month study. Head circumference increased, but not significantly. Three patients were stunted and two were wasted (-2.0 z-score) at baseline while at study end, only one patient was both stunted and wasted. The majority of patients increased in length, head circumference, and weight z-scores during study. Mean (+/-SE) plasma albumin concentration increased from 34+/-2g/L at baseline to 38+/-1g/L at study end. Plasma transthyretin increased from a mean (+/-SE) of 177+/-13 mg/L at baseline to 231+/-15 mg/L at study end. No correlation was found between plasma NH(3) concentrations and medical food intake. Plasma NH(3) concentration was positively correlated with the percentage of Food and Agriculture Organization/World Health Organization/United Nations recommended protein ingested.

CONCLUSIONS

Intakes of adequate protein and energy for age result in anabolism and linear growth without increasing plasma NH(3) concentrations. Medical food intakes did not correlate with plasma NH(3) concentrations.

Anorexia and altered serotonin metabolism in a patient with argininosuccinic aciduria

We studied serotonin metabolism in a metabolically stable 7-year-old girl with argininosuccinic aciduria who had severe anorexia. The CSF concentration of 5-hydroxyindoleacetic acid (HIAA), the metabolite of serotonin, was markedly elevated at 79 ng/ml (normal 33 +/- 11 ng/ml). Altered serotonin metabolism was also reflected in the sleep EEG, which showed decreased REM sleep. Reducing her intake of tryptophan, the precursor of serotonin, from 35 mg/kg/day to 7 mg/kg/day resulted in a decrease in CSF concentration of HIAA to 20 ng/ml and the onset of spontaneous eating for the first time in 4 1/2 years. REM sleep increased from 3% to 9.5% of total sleep time. Two days after increasing tryptophan intake to 25 mg/kg/day, spontaneous feeding stopped, associated with a rise in CSF HIAA to 45 ng/ml. Caloric/carbohydrate intake was found to affect CSF HIAA levels and food intake in an additive manner with tryptophan intake. These observations suggest that altered serotonin metabolism affected feeding behavior in this child, and that this effect could be modified by changing tryptophan or carbohydrate intake.

Prospective prevention of neonatal hyperammonaemia in argininosuccinic acidura by arginine therapy

Argininosuccinic aciduria, due to deficiency of argininosuccinic acid lyase, is generally associated with severe neonatal hyperammonaemia and its neurological sequelae. The cases of two siblings with this autosomal recessive disorder are presented. Both infants were preterm and delivered by Caesarean section for maternal pre-eclampsia. The first infant was not diagnosed until after the development of severe hyperammonaemia and, despite adequate treatment with haemodialysis and arginine infusion, remained comatose for a prolonged period. At 20 months she has profound developmental delays and intellectual impairment. The second infant, whose diagnosis was made antenatally by amniotic fluid analysis, was treated with arginine infusion beginning at 32 h of life and never developed hyperammonaemia. We conclude that early recognition and prompt institution of arginine therapy is an effective regimen for the prevention of neonatal hyperammonaemia in argininosuccinic aciduria.

Metabolic acidosis in the newborn period

In this chapter we have described the metabolic diseases which are known to have caused acidosis during the newborn period. We have also provided some diagnostic and treatment guidelines. The occurrence of acidosis in a newborn baby should initiate several actions, aimed simultaneously at treatment and diagnosis. An initial blood gas determination, accompanied by the results of serum electrolytes and glucose, will, in most instances, separate respiratory from metabolic causes. Finding of an increased anion gap and/or presence of hypoglycaemia should direct attention towards errors in intermediary metabolism.