Nutritional Therapy Improves Growth and Protein Status of Children with a Urea Cycle Enzyme Defect

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


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


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.


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 ± 2 g/L at baseline to 38 ± 1 g/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 NH3 concentrations and medical food intake. Plasma NH3concentration was positively correlated with the percentage of Food and Agriculture Organization/World Health Organization/United Nations recommended protein ingested.


Intakes of adequate protein and energy for age result in anabolism and linear growth without increasing plasma NH3 concentrations. Medical food intakes did not correlate with plasma NH3 concentrations.



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