Wechsler subscale IQ and subtest profile in early treated phenylketonuria.

AIM: Mildly depressed IQ is common in treated phenylketonuria. This study explored whether a particular intellectual ability profile typifies early and continuously treated phenylketonuria and whether component skills comprising the IQ relate to socioeconomic and treatment factors. METHODS: IQ scores were collected retrospectively from variants of the "Wechsler intelligence scale for children" performed at age 8 on 57 children with early treated, classic phenylketonuria. The mental ability pattern underlying IQ was investigated by analysing subscale and subtest scores and dietary factors, such as historical phenylalanine blood concentrations. RESULTS: The children's mean full scale IQ of 91.11 was significantly below the healthy population norm. There was a significant discrepancy between their mean verbal IQ (94.65) and mean performance IQ (89.42), suggestive of a spatial deficit, but the data did not support a biochemical or sociological explanation. Individual Wechsler subtests had no distinctive pattern. Phenylalanine control at age 2 was predictive of overall IQ. At this age, children with annual median phenylalanine < 360 micromol/litre (recommended UK upper limit) had a mean IQ 10 points higher than those above. CONCLUSIONS: Early and continuous treatment of phenylketonuria does not necessarily lead to normalisation of overall IQ. Verbal intelligence in the primary school years appears to normalise if blood phenylalanine is maintained below 360 micromol/litre in infancy, but spatial intelligence may remain poor. However, the discrepancy in skill development is not the result of social status or treatment variables. Perhaps weak spatial intelligence is an ancillary effect of a protective rearing style occasioned by the dietary treatment regimen.     

Repeated adverse fetal outcome in pregnancy complicated by uncontrolled maternal phenylketonuria

Phenylketonuria in pregnancy carries with it an increased risk of spontaneous abortion and development of a fetus that is affected by the maternal phenylketonuria syndrome. This syndrome is characterized by low birthweight, congenital heart disease, microcephaly, childhood growth failure, and cognitive impairment. It is the result of the hyperphenylalaninemia that accompanies the phenylketonuric state, and may therefore be avoided by maintaining maternal serum phenylalanine levels within the normal range. Phenylalanine is an essential amino acid and may be controlled by dietary manipulation. Presented here is a case history of a woman with phenylketonuria who was unable to satisfactorily control her serum phenylalanine levels in each of her three pregnancies. All three children were adversely affected by the fetopathy of the maternal phenylketonuria syndrome, each with evidence of growth failure and impaired neurodevelopment. This patient illustrates the difficulties that may be encountered when providing obstetric care to the woman with phenylketonuria who is not able or not willing to restrict her dietary intake of phenylalanine. The discussion includes consideration of management strategies, including dietary therapy and legal intervention.     

Final intelligence in late treated patients with phenylketonuria

Despite neonatal screening programmes, there is still a number of patients with phenylketonuria who are not diagnosed and start treatment late. The question in this study was to evaluate which factors will contribute, other than the quality and duration of dietary treatment, to final outcome in late treated patients with phenylketonuria. We retrospectively analysed the data of 40 patients with phenylketonuria, of whom 2 patients at 35 and 24 years of age had a normal IQ despite never being treated. In 38 patients starting dietary treatment between 0.7 and 7 years of age, mean IQ/DQ at diagnosis was 52.7 (SD=16) (mean age 2.5 years), final IQ (mean age 33.5 years) was 79.0 (SD=16), the difference was highly significant (P < 0.0001). Important factors for the final intelligence in adult late treated patients with phenylketonuria were onset (r=т.46, P < 0.009) and DQ/IQ (r=0.51, P < 0.002) when dietary treatment was started. Thus, in late treated patients with phenylketonuria, in addition to the quality and duration of treatment, the outcome is mainly influenced by the age of starting treatment and also by the intellectual status of the patient. In one of the two patients with normal intelligence, nuclear magnetic resonance spectroscopy showed that brain phenylalanine was undetectable even though blood phenylalanine was 30 mg/dl. A second metabolic disorder may protect these patients from severe brain damage. Conclusion These data indicate that brain damage in untreated or late treated patients with phenylketonuria is influenced by various genetic factors.     

Wechsler subscale IQ and subtest profile in early treated phenylketonuria

AIM—Mildly depressed IQ is common in treated phenylketonuria. This study explored whether a particular intellectual ability profile typifies early and continuously treated phenylketonuria and whether component skills comprising the IQ relate to socioeconomic and treatment factors.
METHODS—IQ scores were collected retrospectively from variants of the "Wechsler intelligence scale for children" performed at age 8 on 57 children with early treated, classic phenylketonuria. The mental ability pattern underlying IQ was investigated by analysing subscale and subtest scores and dietary factors, such as historical phenylalanine blood concentrations.
RESULTS—The children''s mean full scale IQ of 91.11 was significantly below the healthy population norm. There was a significant discrepancy between their mean verbal IQ (94.65) and mean performance IQ (89.42), suggestive of a spatial deficit, but the data did not support a biochemical or sociological explanation. Individual Wechsler subtests had no distinctive pattern. Phenylalanine control at age 2 was predictive of overall IQ. At this age, children with annual median phenylalanine < 360 µmol/litre (recommended UK upper limit) had a mean IQ 10 points higher than those above.
CONCLUSIONS—Early and continuous treatment of phenylketonuria does not necessarily lead to normalisation of overall IQ. Verbal intelligence in the primary school years appears to normalise if blood phenylalanine is maintained below 360 µmol/litre in infancy, but spatial intelligence may remain poor. However, the discrepancy in skill development is not the result of social status or treatment variables. Perhaps weak spatial intelligence is an ancillary effect of a protective rearing style occasioned by the dietary treatment regimen.
     

Predictors of intelligence quotient and intelligence quotient change in persons treated for phenylketonuria early in life

Ninety-one individuals with phenylketonuria who were treated early in life were followed for as many as 22 years. Regression analyses were used to determine the best predictors of IQ and IQ change. Among treatment-related variables, good dietary control of the blood phenylalanine level stood out as the best predictor of IQ. Diet discontinuation and the natural (off diet) blood phenylalanine level best predicted IQ loss, suggesting that diet continuation may be important for children with natural blood phenylalanine levels greater than 18 mg/dL.     

Biopterin derivatives in normal and phenylketonuric patients after oral loads of L-phenylalanine, L-tyrosine, and L-tryptophan

Plasma biopterin derivatives studied in 10 normal and 21 phenylketonuric children showed a significantly high concentration in the latter group. Biopterin derivatives correlated with plasma phenylalanine concentration, but in normal adults given an oral phenylalanine load the rate of increase with phenylalanine differed from that in phenylketonuric patients. A patient with hyperphenylalaninaemia, not due to phenylketonuria, had an abnormal biopterin derivatives response to phenylalanine distinct from that of patients with classical phenylketonuria. This may be a useful investigation to differentiate some variants of phenylketonuria.     

Biopterin derivatives in normal and phenylketonuric patients after oral loads of L-phenylalanine,L-tyrosine,and L-tryptophan.

Plasma biopterin derivatives studied in 10 normal and 21 phenylketonuric children showed a significantly high concentration in the latter group. Biopterin derivatives correlated with plasma phenylalanine concentration, but in normal adults given an oral phenylalanine load the rate of increase with phenylalanine differed from that in phenylketonuric patients. A patient with hyperphenylalaninaemia, not due to phenylketonuria, had an abnormal biopterin derivatives response to phenylalanine distinct from that of patients with classical phenylketonuria. This may be a useful investigation to differentiate some variants of phenylketonuria.     

Situational analysis of dietary challenges of the treatment regimen for children and adolescents with phenylketonuria and their primary caregivers

A situational analysis was conducted to evaluate challenges with the treatment regimen (a low protein diet and special supplemental formula) for children and adolescents with phenylketonuria (PKU) and their caregivers. A semistructured interview was administered to 19 caregivers and 11 children with PKU to describe formula and dietary problems and their frequency, difficulty, and affective intensity. Information was also gathered on attempted solutions to problems and their perceived effectiveness. Caregivers who rated dietary problems as less frequent, difficult, and emotionally upsetting and strategies as more effective for solving problems had children with significantly lower phenylalanine (Phe) levels, a biological indicator of adherence (i.e., better adherence; all p values <.05). Caregivers who reported using strategies coded as representing an authoritarian parenting style to solve dietary problems were significantly more likely to have lower household incomes and older children with higher Phe levels than were those who did not report such strategies (all p values <.05).     

Intellectual assessment of 111 four-year-old children with phenylketonuria

Of the 216 children with phenylketonuria (PKU) who were initially enrolled in the Collaborative Study of Children Treated for Phenylketonuria, 203 were placed on dietary therapy between 3 and 92 days of age. Of these, 111 are now at least 4 years of age and constituted the sample for the present analysis. Their mean IQ on the Stanford Binet Intelligence Scale was 93 (1972 norms). The children assigned to two treatment groups based on "moderate" and "low" serum phenylalanine levels were comparable on their IQs at age 4, although many of the children could not be maintained in the specified categories. Females scored a significantly higher mean IQ than males (97 vs 90). Those children for whom dietary treatment was initiated during the first month of life scored a mean IQ of 95, compared with 85 for those initially treated from 31 to 65 days. However, the interpretation of dietary inception data may have been contaminated by familial and psychosocial factors. The PKU Collaborative Study is still in progress in 15 clinics located in 11 states.     

Loss of intellectual function in children with phenylketonuria after relaxation of dietary phenylalanine restriction

Fourteen patients with classic phenylketonuria (PKU) were treated with a phenylalanine restricted diet from early infancy. All had satisfactory dietary control, with serum phenylalanine concentrations ranging between 2 to 5 mg/dL. Dietary restriction was discontinued in all these children between ages 5 and 6 years, and a free diet allowed. Developmental testing was performed using the Cattell Infant Intelligence Scales (1 to 2 years), Stanford-Binet Intelligence Scale (2 to 4 years), Wechsler Intelligence Scale for Children (WISC) and the revised version (WISC-R) (less than 5 years). Mean IQ for the group (Stanford-Binet and WISC) at termination of dietary therapy was 104 +/- 13. Four to 7 years after discontinuation of dietary therapy, mean IQ for the group was 90 +/- 13. The severity correlated, to some degree, with duration of unrestricted diet, but not with initial serum phenylalanine concentrations, age at initiation of therapy, or IQ at time diet was discontinued. Several children are experiencing difficulties, both attentional and academic, in school. Two children have had a change in the EEG from normal to abnormal. Neurologic testing performed after 4 to 7 years off diet demonstrated deficits in visual-motor integration or cognitive problem-solving in most children. The mean developmental age for the group for perceptual-motor integration was 1.2 years below the mean chronologic age of the group. This deterioration in intellectual function suggests that discontinuation of the phenylalanine-restricted diet is hazardous for some children with classic phenylketonuria.     

Intellectual development in 12-year-old children treated for phenylketonuria

Intelligence and achievement test scores were evaluated for 95 12-year-old children with phenylketonuria who had begun dietary therapy during the neonatal period. Dietary control of blood phenylalanine below 900 mumol/L was maintained beyond age 10 years in 23 children; 72 others had blood phenylalanine persistently above that level at ages ranging from 18 months to 10 years. Test scores at age 12 years were negatively correlated with the age at initiation of diet and with blood phenylalanine levels from ages 4 to 10 years, and positively correlated with parent IQ scores and the age at loss of dietary control. Children who maintained phenylalanine levels below 900 mumol/L beyond age 10 years showed no deficits in test scores, except for arithmetic, the scores of which declined between ages 6 and 12 years in 90% of the children in this study. These data strongly support a recommendation that dietary restriction of phenylalanine should be maintained through adolescence.     

Deficits in selective and sustained attention processes in early treated children with phenylketonuria — result of impaired frontal lobe functions?

Twenty normally intelligent children with early treated phenylketonuria (PKU) (IQ: mean=101.4, SD=10.0; age: mean=10 years 11 months, SD=1.3 years) and 20 healthy controls, matched for age, sex and IQ, were assessed for their selective (Stroop Task) and sustained attention (Test-d-2). Using positron emission tomography an activation of the frontal lobe during the Stroop task had previously been demonstrated. In addition to the Stroop Task and the Test-d-2, a short-term memory test as a non-frontal-lobe-function-task was administered to all subjects. Group comparisons demonstrated that PKU children had specific deficits in selective and sustained attention, which were significantly correlated with the concurrent serum phenylalanine concentration.Conclusion The results give evidence that even dietary treated children with PKU were suffering from impaired attentional control mechanisms in spite of a normal IQ. The deficits might be the result of impaired frontal lobe functions.     

Serum cholesterol ester fatty acids in 7- and 13-month-old children in a prospective randomized trial of a low-saturated fat, low-cholesterol diet: the STRIP baby project

To evaluate changes that occur in serum cholesterol ester fatty acid composition during the transition from typical infant feeding to a more adult type of nutrition, this study compared the effects on serum cholesterol ester fatty acids of breast milk or formula at the age of 7 mo with effects caused by 6-mo dietary intervention in 137 children. The intervention [Special Turku coronary Risk factor Intervention Project for children (STRIP baby project)] aimed at a reduction of saturated fat intake to 10% of energy after the age of 1 y without purposefully influencing total fat intake. Nutrient intakes were calculated from 3-d food records. At the age of 7 mo, i.e. before dietary education began, milk type markedly influenced dietary and serum cholesterol ester fatty acid composition (mean serum cholesterol ester 16:0 in breastfed vs formula-fed infants, 13.7% vs 12.0%, respectively, p < 0.001; serum cholesterol ester 18:2n-6 50.6% vs 57.6%, p < 0.001). At the age of 13 mo the calculated fat intake of the intervention and control children differed markedly but serum cholesterol ester fatty acid compositions in all children resembled closely those measured in 7-mo-old breastfed infants, e.g. at the age of 13 mo the relative proportions of 18:2n-6 were 49.9% and 51.1% in previously formula-fed intervention and control children, respectively, and 50.3% and 50.1% in previously breastfed intervention and control children, respectively. In conclusion, serum cholesterol ester fatty acid composition reflected differences in dietary fat quality (breast milk or formula) at the age of 7 mo, whereas dietary intervention as applied in the STRIP baby project had only a minimal effect.     

Effect on intelligence of relaxing the low phenylalanine diet in phenylketonuria.

A total of 599 children with phenylketonuria, who had been treated early, were followed up prospectively in order to examine the association between intellectual progress from 4 to 14 years of age and control of phenylalanine concentrations. The phenylalanine rose from around 400 mumol/l during the first four years to above 900 mumol/l by 12 years. The children were divided into two cohorts: cohort I comprised 224 children born in the United Kingdom between 1964 and 1971 and cohort II 375 children born between 1972 and 1978. In a previous study it was shown that by 4 years of age these children already had a mean intelligence quotient (IQ) over half a standard deviation below general population norms, and that IQ fell linearly as average phenylalanine concentrations rose. Multiple regression was used to estimate the size of the associations between IQ at later ages and average phenylalanine concentrations in the periods between assessments, after controlling for previous IQ and phenylalanine control, social class, type of phenylketonuria, and factors relating to diagnosis and early management. For each 300 mumol/l rise in average phenylalanine concentrations for those aged 5 to 8 years IQ at 8 years fell by 4-6 points. This compared with a 7-10 point fall in IQ at 4 years for a similar rise in phenylalanine. After 8 years of age the association between IQ and phenylalanine control disappeared in cohort I but persisted in cohort II and was significant up to 10 years of age, although the association was smaller than at 8 years.     

Variability of reproductive casualty in maternal phenylalaninemia

A biochemical survey of 4,000 parents of mentally retarded children did not identify any mothers with elevated phenylalanine blood levels. This' finding and an analysis of nearly 100 reported cases of maternal phenylalaninemia suggest a low risk of reproductive casualty in phenylalaninemic mothers who somehow escaped the usual effects of phenylketonuria. Recent observation on cases of maternal phenylalaninemia who were detected through unselected screening indicate that the reproductive risk associated with the condition may have been overestimated in the past. This risk is concentrated in mothers who had been affected themselves. Mental level appears to be a stronger predictor of reproductive outcome in phenylalaninemic women than the degree of phenylalaninemia. Selective prenatal intervention based on maternal mental level is not possible, however, where the natural history of the condition has been altered. This is the case in phenylketonuric girls who had been treated during childhood. These girls are now reaching child-bearing age in fast growing numbers, as a result of screening for phenylketonuria. Prenatal intervention is appropriate for all of them until predictors are established that can identify those at risk of reproductive casualty.     

Intellectual development after relaxing the diet at the age of 5 years in typical phenylketonuria]

BACKGROUND. No satisfactory controlled trial has yet been completed on typical phenylketonuria (PKU) patients whose treatment was relaxed at the age of 5 years. METHODS. 27 children having typical PKU were treated before the age of 3 months. The intake of phenylalanine and protein was carefully regulated during the first 5 years of life, after which the treatment was relaxed. All children were evaluated after at least 6 years on the relaxed diet. Their IQ scores and school performance were related to the degree of dietary control and plasma phenylalanine values. RESULTS. The IQ scores at 5 years of age were 100 +/- 10.8. Continued evaluation showed that IQ scores remained unchanged. Poor school performance was twice as frequent as in general population; the deficit in the IQ score of this group was 8 points below that of normal sibs. There was no correlation between plasma phenylalanine and the IQ score after the age of 5 years. The positive control decreased with aged. CONCLUSIONS. Children with typical PKU have an IQ deficit relative to their normal sibs just before relaxing treatment. Good dietary control until 5 years of age, maternal intelligence and continuing evaluation during relaxing diet are the best conditions for optimal intellectual progress. There is no evidence that continued treatment during adolescence is beneficial.     

Problems stemming from pregnancy in a woman with phenylketonuria

A normal infant was born to a 25 year-old mother with phenylketonuria who had never been treated. The mother had been fed a phenylalanine restricted diet for 3 months before the beginning of the pregnancy. Dietary control was maintained throughout the whole gestation. The problems of dietary control in a mentally retarded woman are analysed.     

Breast milk jaundice in premature infants.

In randomised study of 186 preterm infants those fed on maternal or banked breast milk had a significantly higher peak bilirubin concentration and a more prolonged jaundice than infants fed an artificial preterm formula and were over four times more likely to achieve plasma bilirubin values above 200 mumol/l (11.7 mg/100 ml). This dietary effect was seen even in a high risk subgroup of sick ventilated infants below 1500 g who were receiving restricted enteral intakes. We suggest that breast milk jaundice in preterm infants may increase clinical intervention. Our findings are discussed in the light of epidemiological data suggesting an association between moderate hyperbilirubinaemia (greater than 170 mumol/l) and neurodevelopmental outcome.     

URINARY PHENYLALANINE EXCRETION IN HYPERPHENYL-ALANINEMIC CHILDREN

24-hour phenylalanine loading tests were done in 5 children with persistent hyperphenyl-alaninemia off diet. The urinary excretion of phenylalanine were compared to the excretion after loading of phenylketonuric children on diet. Serum phenylalanine of children with persistent hyperphenylalaninemia returned to preloading levels (285 μmol/l) within 24 hours. These children, however, excreted phenylalanine during phenylalanine loading in lesser quantities than patients with phenylketonuria on diet. Serum phenylalanine of phenylketonuric children on diet attained preloading levels (300 μmol/l) approximately 14 days after loading. Thus, the present data do not support the hypothesis that hyperphenylalaninemic patients are phenylketonurics protected by increased urinary excretion of phenylalanine.     

Breastfeeding and brain development

Although biochemical evidence seems to support the fact that more DHA is incorporated into the brain of breastfed infants compared with formula-fed infants, whether the levels of DHA in the brain are clinically significant is unclear. Because randomized trials cannot be done, this issue is difficult to study. The effects of breastfeeding on developmental outcome in term infants seems to be small or insignificant. For otherwise healthy children the potential differences are not clinically relevant; however, these small differences distributed over an entire population might have a significant effect on society. Although significant methodologic concerns exist, the effects of breastfeeding on preterm infants may be greater than those for term infants. Extremely low birth weight, premature infants (< 750-1000 g) have been found to have IQs that are 13 points lower than term controls and a 50% to 60% risk for requiring special-education services when they are in school. In these infants, small improvements in IQ and neurologic function could have a much greater effect. Further study of neurodevelopmental outcome in premature infants fed breast milk compared with those fed preterm formula are indicated. This information should not change the practice of encouraging breastfeeding of term and preterm infants because other advantages to breastfeeding exist.