Intelligence and quality of dietary treatment in phenylketonuria

Article Abstract:

When identified at birth, children with the hereditary defect phenylketonuria may lead reasonably normal lives if they receive appropriate treatment. Their genetic deficiency in the enzyme phenylalanine hydroxylase prevents them from properly metabolizing the amino acid phenylalanine. If this amino acid is not precisely controlled in their diet soon after birth, they will develop severe mental retardation. However, despite dietary control, children with phenylketonuria generally have IQs lower than those of their brothers and sisters, and often have behavioral abnormalities, suggesting that there may be some neurological impairment even among those on appropriate diets. A review of 1,031 children with phenylketonuria identified major factors determining the intellectual performance of children growing up with this metabolic abnormality. Although a previous study failed to find an advantage for stricter control of phenylalanine intake, the present study found a decrease in IQ of roughly four points for each 300 micromoles per liter increase in the blood concentration of phenylalanine. The study also observed a similar decrease in IQ for each five months during the first two years of life that the phenylalanine concentration fell below 120 micromoles per liter. It is not certain that the phenylalanine concentration is the cause of the IQ reduction, as the failure to strictly maintain blood levels may have other causes, which could also influence intellectual development. Nevertheless, the results argue strongly for precise regulation of the level of circulating phenylalanine, and reveal that delays in the initiation of treatment after birth may have serious consequences for normal development. Treatment should begin within three weeks of birth. Although current standards suggest that a phenylalanine blood level of 180-480 micromoles per liter be maintained, the authors recommend reducing the standards to 120-300 micromoles per liter because the study indicates that too little phenylalanine may be harmful as well. Reducing the standard phenylalanine blood levels would require that stricter control be maintained. (Consumer Summary produced by Reliance Medical Information, Inc.)

Care and treatment, Metabolism, Inborn errors of, Inborn errors of metabolism, Developmentally disabled children, Brain diseases, Metabolic, Metabolic brain diseases

---

Pregnancy in phenylketonuria: dietary treatment aimed at normalising maternal plasma phenylalanine concentration

Article Abstract:

Phenylketonuria (PKU) is a genetic disorder that results from a deficiency of the enzyme that converts the amino acid phenylalanine into tyrosine. It causes phenylalanine to accumulate in the blood, which can cause brain damage, mental retardation and seizures. Since phenylalanine crosses the placenta and can reach higher concentrations in the fetal blood than in the maternal blood, pregnant women with PKU are at risk for having babies who are mentally retarded. It has been reported that women who have abnormally high levels of phenylalanine in their blood at the time of conception give birth to infants with smaller heads (measured in terms of circumference). Studies have shown that brain damage associated with PKU can be prevented by reducing the amount of phenylalanine in the diet. On the basis of such findings, it has been suggested that blood levels of phenylalanine should be maintained within the normal range in pregnant women with PKU. To determine if maintaining phenylalanine concentrations within the normal range can result in a normal pregnancy and outcome, a female patient with PKU was maintained on a special diet low in phenylalanine for 10 weeks prior to conception. During pregnancy the amount of phenylalanine in the diet was adjusted to maintain normal blood levels of phenylalanine, and blood levels of phenylalanine were monitored on a weekly basis. The diet was supplemented with tyrosine, vitamins and minerals. The pregnancy proceeded without complications and the results of ultrasound examinations were normal. An apparently healthy infant weighing 8.6 pounds, with a head circumference within the 50th to 75th percentile, was born at week 41 of pregnancy. The results of this study suggest that maintaining blood levels of phenylalanine within the normal range prior to and after conception may allow women with PKU to have normal pregnancies. Further studies with larger numbers of women are needed to verify these findings. (Consumer Summary produced by Reliance Medical Information, Inc.)

Prevention, Food and nutrition, Pregnant women, Mental retardation, Blood chemical analysis, blood

---

Effect on intelligence of relaxing the low phenylalanine diet in phenylketonuria

Article Abstract:

Phenylketonuria is a genetic disorder characterized by the inability to oxidize the amino acid phenylalanine into tyrosine due to a defective enzyme. Previous studies show that, despite early treatment, children with phenylketonuria had an average intelligence quotient (IQ) at four years of age that was less than that of the general population. Early treatment was also associated with the development of behavior problems, particularly in children with high phenylalanine levels. These findings suggest that children with phenylketonuria have a persistent elevation of phenylalanine levels, despite early treatment, which results in continued impairment of nerve function. If treatment is discontinued after four years of age, intelligence or progress in school declines further. Treatment is often discontinued because the diet requires restrictions on natural foods and replacement with unappetizing substitutes. The relation between phenylalanine levels and intellectual progress between 4 and 14 years was assessed in 599 children with phenylketonuria, who received early treatment. The results showed that for every increase in phenylalanine levels of 300 micromoles per liter for children between five and eight years, the IQ dropped between four and six points at eight years old. A similar rise in phenylalanine levels was associated with a drop in IQ at four years between 7 and 10 points. The relation between IQ and phenylalanine levels diminished after eight years in children born between 1964 and 1971, but persisted to age 10 years in children born between 1972 and 1978. (Consumer Summary produced by Reliance Medical Information, Inc.)

Psychological aspects, Health aspects, Measurement, Complications and side effects, Intelligence (Psychology), Intellect, Phenylalanine, Low-phenylalanine diet, Low phenylalanine diet

Similar abstracts:

• Abstracts: Trace element nutrition status and dietary intake of children with phenylketonuria. Trace element status in multiple sclerosis
• Abstracts: Reappraisal of thyroxine treatment in primary hypothyroidism. Autoimmune chronic active hepatitis in a family
• Abstracts: Seizures and other neurologic sequelae of bacterial meningitis in children
• Abstracts: Falls in older persons: causes and interventions. Perceived quality of life and preferences for life-sustaining treatment in older adults
• Abstracts: Epidemiology and prevention of AIDS among intravenous drug users

This website is not affiliated with document authors or copyright owners. This page is provided for informational purposes only. Unintentional errors are possible.