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Bone mineral status in children with phenylketonuria--relationship to nutritional intake and phenylalanine control
M P McMurry1, G M Chan, C O Leonard
1Clinical Research Center, School of Medicine, University of Utah, Salt Lake City.
Insights
Phenylketonuria (PKU) patients show normal bone mineral content in childhood with strict diets. Older PKU patients with lower dietary compliance risk reduced bone mineral content.
Area of Science:
- Biochemistry
- Pediatrics
- Nutrition Science
Background:
- Phenylketonuria (PKU) is a genetic disorder requiring strict dietary management.
- Bone health is a concern in children with chronic metabolic conditions.
Purpose of the Study:
- To assess the mineral status and bone mineral content in children and adolescents with PKU.
- To investigate the relationship between dietary compliance, phenylalanine levels, and bone health in PKU patients.
Main Methods:
- Bone mineral content was measured using single-photon densitometry of the distal radius.
- Plasma concentrations of various minerals, alkaline phosphatase, and parathyroid hormone were analyzed.
- Dietary compliance was assessed, and blood phenylalanine levels were monitored.
Main Results:
- Younger PKU children with strict diets exhibited normal bone mineral content development.
- Older PKU patients (age > 8 years) frequently had below-normal bone mineral content.
- Higher blood phenylalanine levels in older patients correlated with decreased dietary compliance.
- PKU patients showed decreased plasma concentrations of alkaline phosphatase, magnesium, and parathyroid hormone.
- Subnormal plasma zinc and copper levels were common, though red blood cell zinc was normal.
Conclusions:
- Dietary compliance is crucial for normal bone development in young PKU patients.
- Older PKU patients with suboptimal dietary adherence are at risk for diminished bone mineral content.
- PKU management should consider monitoring bone health and key mineral levels, especially in older patients with variable compliance.
Abstract:
The mineral status in phenylketonuria (PKU) was measured by single-photon densitometry of the distal radius and plasma concentrations in 26 subjects. Bone mineral content increased normally with age in the younger children despite strict dietary restrictions. Subjects aged greater than 8 y, however, were frequently below the normal curve for bone mineral content. Blood phenylalanine concentrations were significantly higher in the older group of subjects and this correlated with decreased compliance with dietary prescriptions. PKU children had significantly decreased plasma concentrations of alkaline phosphatase, magnesium, and parathyroid hormone. Subnormal concentrations of plasma zinc and plasma and red blood cell (RBC) copper were common, but RBC zinc was normal. We conclude that compliance with dietary therapy for PKU is associated with normal bone mineral development in young children. Older patients with PKU who follow the diet less carefully are at risk for low bone mineral content.