Physical Growth and Nutritional Status of Children with Phenylketonuria

Abstract

Phenylketonuria (PKU) is a genetic disorder of phenylalanine (Phe) metabolism. Conversion of Phe to tyrosine is impaired resulting in an accumulation of Phe and its metabolites in the blood, causing brain damage. Presently, through neonatal screening and careful monitoring and controlling of blood Phe level, mental development of these children is usually normal. Dietary management includes the controlled intake of low protein foods and the intake of low Phe or Phe-free amino acid mixture formula. Due to elimination of high protein foods and inadequate intake of formula, their protein intakes are quite low. Therefore, the study was designed to evaluate the physical growth, food intake, and nutritional status. Three male and three female children with PKU aged 3–16 years were subjects of this study. Three-day food diary, formula intakes, height and weight, and blood parameters were evaluated. This study showed that these children had stunted physical growth suggesting inadequate protein and energy intakes. Five of the six children were below the twenty-fifth percentile for both height and weight for their ages and sex. The mean percentile was 23.7 ± 23.7 and 24.2 ± 18.4 for the height and weight, respectively. Their protein intakes were also low; the mean protein intake was 62 ± 15 percent of their recommended levels. Other low intakes included calcium, phosphorus, and zinc. Blood analysis showed that these children had normal levels of glucose, hemoglobin, hematocrit, calcium, and total serum protein. The abnormal values included high serum albumin, low blood urea nitrogen, low creatinine, and low or high cholesterol. Younger children, aged 3 and 4 years, had a better control of blood Phe levels (6 and 6.2mg/dl). Older children, aged 8, 9, 12 and 16, had high levels of blood Phe (9.5, 13.9, 16.9, 17.5mg/dl), indicating they were in the catabolic stage due to inadequate protein and caloric intakes. This study demonstrates that careful monitoring of their diets and increasing protein intake are required. Increasing protein intake of their diets with a controlled amount of Phe is under investigation in a separate study.