Diet discontinuation policies and practices of PKU clinics in the United States

The challenge of adults with phenylketonuria who have been lost to care; a single center's attempt to reach those diagnosed with PKU over 60 years of newborn screening

Background

Those diagnosed with PKU in the early years of newborn screening (NBS) were often discharged from clinic in childhood. Long-term lost to clinic patients may be impacted by untreated PKU and uninformed about current recommendations. We aimed to contact adults away from clinic for 5-50+ years, share current recommendations, offer clinical care, and elicit factors underlying not returning to clinic.

Methods

Former patients were identified and offered a virtual meeting with a physician and dietitian for structured interview and education about current guidelines and treatments.

Results

We identified 53 eligible patients who had PKU and had not returned to clinic in ≥5 years. Of those 53, 27 were successfully contacted, 16 completed the educational intervention, and 5/16 returned to clinic. Reasons for having been away from clinic included discharge from clinic in childhood and inadequate insurance coverage. Experiences varied and some denied negative impacts after diet discontinuation. Individuals expressed a desire for convenient treatments that aligned with overall health goals. Most participants who completed the educational intervention expressed interest in returning to clinic; however, most did not return within the timeframe of the project. All 27 individuals successfully contacted agreed to be re-contacted with future updates or research opportunities.

Discussion

We successfully contacted half of individuals identified as having been lost to clinic follow-up long-term. Limitations included inability to make initial contact, and unwillingness to re-engage by some we reached. Those who agreed to participation desired ongoing PKU clinic and community connection. This experience will inform our process to engage current patients and re-engage those currently lost to care.

Adult PKU Clinics in the UK-Users' Experiences and Perspectives

Adults with PKU require life-long management, and ideally, their care should be in a specialised adult metabolic clinic. Their outcomes and co-morbidities have received much attention, but data are lacking on their experience, satisfaction and expectations about the care they receive. This survey reports the experiences and care adults with PKU receive from specialist metabolic clinics in the UK. The online survey developed by the UK NSPKU (National Society for Phenylketonuria), was placed on the NSPKU website from February 2021 to December 2022, and was completed by adults with PKU (≥18 years) or their carers/family members. Sixty-five adult PKU patients and 9 caregivers of adult patients completed the questionnaire (63% female in total). Only 32% of respondents were following a Phe-restricted diet with protein substitute intake as prescribed; the rest were partially adherent or not on dietary restrictions. Nineteen per cent (n = 14/74) had not been reviewed in clinic for two years. Half of the respondents (50%) described their experience in adult clinics as "good". Half of the patients were unable to contact their dietitians with questions or concerns, and only 24% considered that they received adequate support. Clinic reviews usually included anthropometric (82%) and dietary assessments (64%), discussion on management of PKU in daily life (78%) and a blood test (71%). Eighty-eight per cent reported they had at least one neurocognitive, mental health or behavioural co-morbidity but less than half of the patients reported an assessment on their neurocognitive functioning or mental health issues. Adult male patients appeared to have less detailed clinic review than females. Less than half (44%) of the respondents reported that they performed a blood spot for blood Phe at least monthly, but only 32% considered they had been informed about the risk of high Phe levels in adulthood. Although time, cost and stress related to travelling were barriers to a face-to-face review, more than 40% of patients had concerns about remote appointments. The frequency and extent of monitoring of adults with PKU, attending specialist adult services, were less than those specified by the PKU European guidelines. The care of women of reproductive age is prioritised over men. Adult metabolic health services require further attention, development and resources to provide a high standard and equitable service to patients with PKU.

Sleeve gastrectomy is feasible in obese patients with phenylketonuria: A case report and literature review

INTRODUCTION AND IMPORTANCE

Patients with phenylketonuria (PKU) exhibit a high incidence of obesity. Currently, bariatric surgery remains the most effective long-term treatment for obese patients. However, limited data regarding the applicability of bariatric surgery to obese patients with PKU have been reported in the literature.

CASE PRESENTATION

A case involving a young woman, in whom sleeve gastrectomy was performed to manage obesity that was resistant to conservative therapy, is presented herein.

CLINICAL DISCUSSION

The present report is the first to describe sleeve gastrectomy in an obese patient with PKU. The surgery proceeded without complications. Furthermore, the patient's phenylalanine levels remained under control for the first 3 months after surgery, with no major neurological complications. The diet prescribed in the first few months after surgery is complex; nevertheless, it is feasible to follow if supervised by a dietary team specialised in rare metabolic diseases.

CONCLUSION

Bariatric surgery in this patient with PKU did not result in any major complications. Surgery is feasible but it is important for the dietetic team involved to have expertise in PKU management.

Newborn screening 50 years later: access issues faced by adults with PKU

Fifty years after the implementation of universal newborn screening programs for phenylketonuria, the first disease identified through newborn screening and considered a success story of newborn screening, a cohort of adults with phenylketonuria treated from birth provides valuable information about effects of long-term treatment for inborn errors of metabolism in general, and phenylketonuria specifically. For phenylketonuria, newborn screening allows early implementation of the phenylalanine-restricted diet, eliminating the severe neurocognitive and neuromotor impairment associated with untreated phenylketonuria. However, executive function impairments and psychiatric problems are frequently reported even for those treated early and continuously with the phenylalanine-restricted diet alone. Moreover, a large percentage of adults with phenylketonuria are reported as lost to follow-up by metabolic clinics. While a group of experts identified by the National Institutes of Health convenes to update treatment guidelines for phenylketonuria, we explore individual patient, social, and economic factors preventing >70% of adult phenylketonuria patients in the United States from accessing treatment. As more conditions are identified through newborn screening, factors affecting access to treatment grow in importance, and we must continue to be vigilant in assessing and addressing factors that affect patient treatment outcomes and not just celebrate amelioration of the most severe manifestations of disease.

Diet, sensitive periods in flavour learning, and growth

Diet in early infancy has an impact on early growth and the formation of flavour preferences, as well as on later life health outcomes. Although breast milk is the preferred source of nutrition during infancy, more than half of American infants receive infant formula by the age of 4 months. As a group, formula-fed infants weigh more by the age of one year and have a greater risk for later obesity than breastfed infants. However, a recent randomized study found that, when compared to breastfed infants, infants fed an extensively hydrolysed protein formula (ePHF) had more normative weight gain velocity than infants fed cow's milk formula (CMF). Therefore, grouping all formula-fed infants together with respect to certain health outcomes such as obesity may not be appropriate. Scientific evidence also suggests that there are sensitive periods for flavour learning. Infants become familiar with and learn to accept the flavours they experience through their mother's amniotic fluid and breast milk as well as formula. These early experiences influence flavour preferences of children that may affect food choices and therefore later life health. Further research on the influence of early diet on growth, flavour preferences, and food choices is imperative.

Perspectives on dietary adherence among women with inborn errors of metabolism

Adherence to highly restrictive diets is critical for women of childbearing age who have inborn errors of metabolism such as phenylketonuria. The purpose of this study was to explore attitudes about diet, barriers to and facilitators of dietary adherence, and experiences with the health care system in promoting dietary adherence among adolescent and adult women with inborn errors of metabolism to identify policy-level interventions to improve adherence. We analyzed the results of four focus groups including a total of 19 women between the ages of 12 and 52 years with phenylketonuria, methylmalonic acidemia, or maple syrup urine disease attending an educational summer camp in 2008. Themes were identified after independent analysis of transcripts. Most participants were highly knowledgeable about their dietary requirements and some could describe their own specific negative experiences of nonadherence. Many reported specific challenges, such as feelings of being different, that they experienced in elementary and middle school. Friends and family play an important role in maintaining dietary adherence. Participants identified one registered dietitian in particular who has played an important supportive role. Insurance coverage for medical foods was a common concern. Most participants identified concerns about transitioning from pediatric to adult medical services. We identified four specific strategies for future evaluation that may improve dietary adherence and health outcomes for women and their potential offspring: symptom-based dietary monitoring for some, educating school officials about medical diets, expanding the role of registered dietitians; and assisting with the transition from pediatric to adult health care providers.

Flavor programming during infancy

OBJECTIVE

Although individuals differ substantially in their flavor and food preferences, the source of such differences remains a mystery. The present experimental study was motivated by clinical observations that early experience with formulas establishes subsequent preferences.

DESIGN

Infants whose parents had chosen to formula-feed them were randomized into 1 of 4 groups by the second week of life. One group was assigned to be fed a milk-based formula (Enfamil), whereas another was assigned to be fed (Nutramigen), a particularly unpleasant-tasting protein hydrolysate formula. The remaining groups were assigned to be fed Nutramigen for 3 months and Enfamil for 4 months; the timing of exposure differed between the groups. After 7 months of exposure, infants were videotaped on 3 separate days while feeding, in counterbalanced order, Enfamil, Nutramigen, and Alimentum, a novel hydrolysate formula.

RESULTS

For each of the 4 interrelated measures of behavior (intake, duration of formula feeding, facial expressions, and mothers' judgments of infant acceptance), previous exposure to Nutramigen significantly enhanced subsequent acceptance of both Nutramigen and Alimentum. Seven months of exposure led to greater acceptance than did 3 months.

CONCLUSIONS

The bases for clinical difficulties in introducing hydrolysate formulas during older infancy are clarified in this study. More broadly, variation in formula flavor provided a useful model for demonstrating experimentally the effects of long-term exposure differences on later acceptance. Such early variation, under more species-typical circumstances (eg, via exposure to different flavors in amniotic fluid and mothers' milk), may underlie individual differences in food acceptability throughout the life span.

Flavor experiences during formula feeding are related to preferences during childhood

As part of a program of research designed to investigate the long-term effects of early feeding experiences, the present study exploited the substantial flavor variation inherent in three classes of commercially available infant formulas and determined whether flavor preferences during childhood differed as a function of the class of formula (i.e., milk, soy, hydrolysate) that 4- to 5-year-old children were fed during their infancy. Age appropriate, game-like tasks that were fun for children and minimized the impact of language development were used to examine their preferences for a wide range of food-related odor qualities including infant formulas, as well as the flavor of milk-based and hydrolysate formulas and plain, sour- and bitter-flavored apple juices. Formula type influenced children's flavor preferences when tested several years after their last exposure to the formula. When compared to children who were fed milk-based formulas (n=27), children fed protein hydrolysate formulas (n=50) were more likely to prefer sour-flavored juices, as well as the odor and flavor of formulas, and less likely to make negative facial expressions during the taste tests. Those fed soy formulas (n=27) preferred the bitter-flavored apple juice. That the effects of differential formula feeding also modified children's food preferences is suggested by mothers' reports that children fed hydrolysate or soy formulas were significantly more likely to prefer broccoli than were those fed milk formulas. These data are consistent with the hypothesis that flavor experiences influence subsequent flavor preferences even several years following the early experience.

Barriers to successful dietary control among pregnant women with phenylketonuria

PURPOSE

The teratogenic effects of maternal PKU are preventable, yet affected babies continue to be born. This study's purpose was to identify barriers to successful dietary control among pregnant women with PKU.

METHODS

An interview-based study was conducted of women with PKU who were known to metabolic disease clinics in three states and pregnant during 1998 to 2000. Medical records were used to document timing of metabolic control.

RESULTS

Of 24 women in the study, only 8 (33%) initiated the diet before pregnancy. Of 22 medical records received, only 12 (55%) indicated control of blood phenylalanine levels before 10 weeks' gestation. Risk factors for late dietary control included young age and belief that treatment costs complicated the diet. Although all of the women expressed confidence in the metabolic clinic staff, few perceived their obstetricians were knowledgeable about the maternal PKU diet. Of 13 women enrolled in state-based assistance programs, 9 (69%) reported proof of pregnancy was required for eligibility. Many women using private insurance reported their insurers were unwilling to pay for medical foods. When the data were stratified according to state of residence, differences were observed in the rate of live-born infants, prepregnancy medical food use, average travel time to the metabolic clinic, and gestational week when metabolic control was achieved.

CONCLUSION

Our study's findings may be used to target educational messages to women with PKU and to direct future research directions. For example, obstetric knowledge of maternal PKU needs further evaluation. Discrepancies should be resolved between maternal PKU medical recommendations and the policies of third party-payers. The disparities in financial assistance and services available to pregnant women with PKU residing in different states should be examined further.

Effect of genotype on changes in intelligence quotient after dietary relaxation in phenylketonuria and hyperphenylalaninaemia

BACKGROUND

Associations between genotype and intellectual outcome in patients with phenylketonuria are complicated because intelligence is influenced by many variables, including environmental factors and other genetic determinants. Intellectual changes with age, both on and after relaxation of diet, vary within the patient population. This study aims to determine whether a significant association exists between genotype and change in intelligence after relaxation of diet.

METHODS

125 patients with hyperphenylalaninaemia and phenylketonuria whose diet was relaxed after 8 years of age. Verbal, performance, and full scale intelligence quotients at 8, 14, and 18 years were expressed as standard deviation scores (IQ-SDS), and genotype as predicted residual enzyme activity (PRA) of phenylalanine hydroxylase.

RESULTS

IQ-SDS at 8, 14, and 18 years were significantly below normal; no association was found between PRA and IQ-SDS. Significant reductions in verbal and full scale IQ-SDS occurred between 8 and 14 years and 8 and 18 years. There was a significant association between PRA and the reduction in verbal, performance, and full scale IQ between these years. Multiple regression analysis of 18 year results, using 8 year results as covariates, supported the association between PRA and IQ-SDS; after adjustment for phenylalanine control, both up to and after the age of 8 years, the full scale IQ-SDS at 14 and 18 years was 0.15 higher for each 10% increase in PRA.

CONCLUSIONS

Genotype might be useful in predicting the likelihood of intellectual change in patients with hyperphenylalaninaemia and phenylketonuria whose diet is relaxed after the age of 8 years.

Cardiovascular defects among the progeny of mouse phenylketonuria females

In a genetic mouse model of human phenylketonuria we have examined the offspring of hyperphenylalaninemic mothers for the presence of cardiovascular defects, an important feature of the pathology of the human maternal phenylketonuria syndrome. Beginning at 14.5 d after conception (75% through gestation), a variety of cardiovascular defects became apparent among the progeny of the hyperphenylalaninemic females. These defects ranged from mild to serious and correlated with the maternal but not the fetal Pah genotype. Nearly all of the defects were vascular, however, whereas the most reported in humans so far have been cardiac. The predisposing biochemical condition in this mouse disease model seems to be the same as in the human disease; elevated maternal blood phenylalanine levels concentrated across the placental barrier to produce a teratogenic developmental environment. This model for congenital cardiovascular defects should enhance two related areas of research. 1) It should allow a more thorough investigation of the relationship between maternal diet and maternal phenylketonuria birth defects, and 2) it should provide an experimental tool to gain insight into the normal process of cardiovascular development.

Phenylketonuria: current dietary treatment practices in the United States and Canada

OBJECTIVE

A survey of treatment centers for phenylketonuria (PKU) in the United States and Canada was undertaken regarding current practices of dietary treatment of PKU.

METHODS

A total of 111 centers, who follow more than 6,950 patients with PKU responded to the survey.

RESULTS

The majority of the centers, 87%, favor life-long dietary control of phenylalanine intake. The survey found lack of uniformity regarding acceptable range of blood phenylalanine levels. The frequency of clinic visits varied and became less frequent as patients got older. Although most of the clinics recommend diet for life, only one-third of the clinics follow patients beyond the age of 18 years, therefore, it is unclear who manages these patients beyond that age. The survey also showed a high number of families with children who were reported for medical neglect (3.0% compared to < 0.06% in the general population). Because of dietary noncompliance, 1% of the children were removed from the home.

DISCUSSION

The survey points to the common treatment goal of diet for life for patients with PKU and underscores the need for uniform guidelines for achieving this goal.

Long-term follow up of patients with classical phenylketonuria after diet relaxation at 5 years of age. The Paris Study

The age for discontinuing dietary treatment of phenylketonuria (PKU) has been a worldwide source of controversy for many years. It is the reason we report here the results of a prospective, controlled study in which the diet was relaxed at 5 years of age in 31 so far well-treated children with classical PKU. The increase of phenylalanine (Phe) plasma levels to about 1500 mumol/l (25 mg/dl) after relaxing the diet was not associated with any significant decline of intellectual performance as measured by the Wechsler scores. Paired comparisons at 7-8 years and 11-13 years of age (n = 12) have shown WISC scores of 102.6 +/- 16.2 and 104.8 +/- 16, respectively, which were not significantly different. Similarly, paired comparisons at 9-10 years and 14-16 years (n = 6) did not demonstrate a significant loss of IQ points (107.7 +/- 13 vs 104.8 +/- 18). Of course, it is possible to argue that we should have observed an increase in IQ with increasing age in our patients and that the absence of deterioration cannot be considered by itself as a good result. Nevertheless, it cannot be excluded that the subtle but global intellectual impairments that have been documented in early-treated subjects are, to a very substantial degree, determined in the pre-school years, long before there is any question of stopping or relaxing the diet.

Neuropsychological effects of subsequent exposure to phenylalanine in adolescents and young adults with early-treated phenylketonuria

Severe mental handicap in phenylketonuria (PKU) can be prevented if dietary treatment is implemented at birth. Controversy remains about the optimum age for terminating treatment. A group of adolescents and young adults with PKU from the West of Scotland Register was identified which had received early treatment, been well-controlled on diet, ceased treatment at 10 years old and subsequently were hyperphenylalaninaemic for 3 years or more. They were given a battery of neuropsychological tests and their results were compared with those of on-diet subjects with PKU and normal controls. The findings generally supported the view that dietary cessation at age 10 is sufficient to prevent a substantial reduction of cognitive and motor ability, and that the central nervous system is probably mature enough to withstand the toxic effects of high blood phenylalanine by then. However, there were minor indications, in keeping with Welsh et al.'s hypothesis [M.C. Welsh, B.F. Pennington, S. Ozonoff, B. Rouse & E.R.B. McCabe (1990) Neuropsychology of early-treated phenylketonuria: specific executive function deficits.

Phenylketonuric patients decades after diet

Nineteen early-treated phenylketonuric patients, whose diet was discontinued between 4.5 and 13 years of age, and who have been off the diet for 12-28 years, were reassessed in 1992-93. There was little change in mean IQ between end of diet and follow-up, less than one IQ point on the average, with no change for any individual exceeding 12 IQ points. Both prior and current IQ correlated slightly negatively with mean phenylalanine (Phe) concentration, and positively with parents' education. The phenylalanine level at follow-up was significantly lower on average by about 900 mumol/L. Five of the subjects (26%) have evidence of mental disease. However, the data suggest that the discontinuation of the diet did not cause intellectual deterioration. Nonetheless, the patients' intellect cannot be the only consideration for maintenance of diet. The occurrence of psychopathology among phenylketonuric patients and the possible unknown effects of toxic elevation of phenylalanine during their lifetime suggest the need to maintain the diet. The use of DNA for diagnostic and prognostic purposes might assist in decisions about dietary quality and duration, and in anticipation of psychopathology.

The use of gelatin capsules for ingestion of formula in dietary treatment of maternal phenylketonuria

Maternal phenylketonuria (PKU) represents a high risk for birth defects, including mental retardation, in offspring. Thus, it could cancel gains represented by the prevention of PKU-induced mental retardation in the current generation. Effective dietary treatment of maternal PKU pregnancies could avoid this potentially tragic occurrence. However, dietary compliance is often difficult because a necessary component of the diet, medical nutritional formulas, often have an unpleasant taste and odour. We treated the second pregnancy of a phenylketonuric women who had required extended hospitalization during her first pregnancy because of poor formula tolerance, and who had similar difficulty in the second pregnancy. To alleviate this problem, we developed a system whereby she could pack the formula into gelatin capsules for ingestion. Packing and ingestion of 20 capsules required less than 30 minutes three times a day. With capsules her blood phenylalanine level was almost always within the recommended range of 120-360 mumol/L (2-6 mg/dl) and hospitalization was not required. The phenylalanine content of the capsules was easily accommodated by a small reduction in allowable food. Other amino acid levels, including tyrosine and other essential nutrient levels, were normal. We believe that using gelatin capsules for formula ingestion can be very beneficial in the management of maternal PKU pregnancies and could be extended to the dietary treatment of other inborn errors of metabolism.

Insurance coverage of special foods needed in the treatment of phenylketonuria

Optimal medical management of phenylketonuria (PKU) requires the use of special low-phenylalanine foods for many years. For women with PKU, elevated maternal blood levels of phenylalanine even at conception can lead to fetal damage. Despite this need, private health insurance, Medicaid, and other public health programs often exclude the cost of these foods from their benefits. The New York State Department of Health conducted a survey of metabolic disorders treatment centers to elucidate the problems PKU patients have obtaining and paying for the special foods essential to their care. Payment for special foods was denied to nearly half of those with private health insurance policies and was covered for only 10 percent of Medicaid-eligibles. A public program for children with special health care needs covered these food costs in upstate New York but not in New York City. There is no program of assistance for adults who are not eligible for Medicaid and who do not have private insurance coverage of special foods. At present, many private health insurance policies and public programs do not cover the costs of low-phenylalanine foods other than infant formula. Payment for this essential part of the management of PKU should be mandated for all public programs for persons with chronic illnesses, public medical assistance (Medicaid) programs, and private health insurance. There is a need for a public program to assist adults with PKU who are not eligible for Medicaid and who do not have health insurance that covers these costs.

Agoraphobia in phenylketonuria

We describe agoraphobia as a complication of phenylketonuria (PKU) in young adults. The five patients have classic PKU and received phenylalanine-restricted diet only in childhood. Only one has normal intelligence. All but one were also depressed. All were anxious. Three of the five had initiated the phenylalanine-restricted diet after 3 months of age. Two returned to the phenylalanine-restricted diet with dramatic reduction of symptoms. The frequency of manifestations of agoraphobia was also examined in 50 young women with PKU enrolled in a longitudinal study of psychosocial factors in maternal PKU, 47 of their acquaintances and 49 women with diabetes. All were administered a test of agoraphobic-avoidant behaviour. The women with PKU appeared to be more prone to social withdrawal and fear of leaving home. Twenty per cent were within the agoraphobia range of the Mobility Inventory. Those still on diet and those with non-PKU hyperphenylalaninaemia reported less avoidant behaviour than those who had terminated the diet in childhood. These results suggest that young adults with PKU are at risk for agoraphobia but that return to the phenylalanine-restricted diet may be an effective treatment.

Aspartame ingestion with and without carbohydrate in phenylketonuric and normal subjects: effect on plasma concentrations of amino acids, glucose, and insulin

Seven subjects homozygous for phenylketonuria (PKU) and seven normal subjects were administered four beverage regimens after an overnight fast: unsweetened beverage, beverage providing carbohydrate (CHO), beverage providing aspartame (APM), and beverage providing APM plus CHO. The APM dose (200 mg) was the amount provided in 12 oz of diet beverage; the CHO was partially hydrolyzed starch (60 g). Plasma amino acid concentrations were determined after dosing and the molar plasma phenylalanine (Phe) to large neutral amino acid (LNAA) ratio calculated. APM administration without CHO did not increase plasma Phe concentrations over baseline values in either normal or PKU subjects (5.48 +/- 0.85 and 150 +/- 23.0 mumols/dL, respectively). Similarly, the Phe/LNAA did not increase significantly. Ingestion of beverage providing APM and CHO did not significantly increase plasma Phe concentrations over baseline values in either normal or PKU subjects. However, ingestion of beverage providing CHO (with or without APM) significantly decreased plasma levels of valine, isoleucine, and leucine 1.5 to 4 hours after dosing in both normal and PKU subjects, thereby increasing the Phe/LNAA ratio significantly. These data indicate that changes noted in Phe/LNAA values after ingestion of beverage providing APM plus CHO were due to CHO. The plasma insulin response to beverage providing CHO (with or without APM) was significantly higher in PKU subjects than in normals.

Maternal phenylketonuria and hyperphenylalaninemia: implications for medical practice in the United States

The risk of maternal phenylketonuria and hyperphenylalaninemia syndrome, a preventable cause of severe birth defects and retardation with a near 100% recurrence risk if untreated, is increasing in the United States. The reasons for this are reviewed. Women with hyperphenylalaninemia and those with phenylketonuria diagnosed and treated at birth are intellectually normal, as are some women with undiagnosed phenylketonuria. Both groups are at risk for maternal phenylketonuria syndrome in their offspring if blood phenylalanine levels are not controlled by diet during pregnancy. The problems and pitfalls of suspecting, diagnosing, and managing the condition are discussed. Suggested strategies for reversing the increasing trend include the greater use of genetic registers, increased clinical awareness, and some form of rescreening. The advantages and costs of rescreening a subset of pregnant women or all pregnant women at or before their first registration are examined.

The New England Maternal PKU Project: identification of at-risk women

Young women with phenylketonuria (PKU) are at risk for bearing children with mental retardation, microcephaly, heart defects, and low birthweight. These effects may be prevented if a low phenylalanine diet is maintained prior to and throughout pregnancy. This report describes the procedures of the New England Regional Maternal PKU Project for identifying and locating this population of at-risk women. Newborn screening records, routine umbilical cord blood screening, and PKU Clinic records provided most of the identifying information. We identified 235 women with hyperphenylalaninemia, ages 12 to 44 years. Of these, 183 had PKU or atypical PKU while 52 had non-PKU mild hyperphenylalaninemia. The 235 women represent 88 per cent of the expected number of women with hyperphenylalaninemia in New England. We identified more than the expected number of those with PKU but only 57 per cent of the expected number with mild hyperphenylalaninemia. Developing a national registry, as well as screening women who utilize birth control clinics or prenatal clinics, may be helpful. Implementing routine umbilical cord blood screening programs may be beneficial in efforts to identify women with hyperphenylalaninemia who have had a child and may want more children in the future.

Long-term development of intelligence (IQ) and EEG in 34 children with phenylketonuria treated early

In 34 children with phenylketonuria (PKU) treated early the prognostic value of the age on institution of the diet (within the first 3 months of life) and of the quality of dietary treatment was determined in two different ways: 1) following intelligence closely (IQ) and (2) evaluating the EEG development up to their 12th (n = 34) and 15th (n = 18) years of life as appropriate. In general, IQ scores were found to be normal from the 4th-15th years of life. In our group of patients there was no effect on the IQ of the timing of diet onset. Children with "strict" dietary control showed a significantly higher IQ than those with "loose" control. One hundred and fifty-four EEGs (10/20 system, awake with eyes closed) were recorded at intervals of 2 years and conventionally evaluated. The development of alpha-activity was found to be normal. Beta-activity was enhanced. Abnormal EEG findings like general slowing and generalized paroxysmal activity (GPA) with or without spikes were more frequent in children with PKU than in controls, with the exception of focal abnormalities. EEG abnormalities increased with advancing age independently of IQ development and showed no relation to either the age at the onset nor the quality of dietary treatment.

Effect of age at loss of dietary control on intellectual performance and behavior of children with phenylketonuria

We determined the effect on intellectual performance and behavior of the age at which dietary control was lost in 119 10-year-old children with phenylketonuria (PKU) who had started on a diet low in phenylalanine before the age of 65 days. The children's diets were considered to be out of control when their blood phenylalanine concentration persistently exceeded 15 mg per deciliter. The age at which control was lost was the best, and frequently the only, predictor of the child's IQ at the age of 8 or 10 years and of the deficit in the child's IQ as compared with those of his or her unaffected siblings or parents. The age at which control was lost was also the best predictor of the deficit in scores on the Wide Range Achievement Test of children with PKU at the age of eight, as compared with their unaffected siblings, and of behavior problems (Louisville Behavior Checklist). Variables that were not significant included the maximal phenylalanine concentration before dietary therapy, the age at which treatment was started, and the family's coping abilities. The greatest deficiencies in all of these outcomes were observed among children who were out of dietary control before the age of six years. The highest correlation between the IQs of the children with PKU and their respective parents was observed among the children still on the diet at the age of eight years; the lowest, among those who had poor dietary control before the age of six. These findings suggest that phenylalanine restriction should continue after the age of eight years in children with PKU.

Extensive restriction site polymorphism at the human phenylalanine hydroxylase locus and application in prenatal diagnosis of phenylketonuria

A total of 10 restriction site polymorphisms have been identified at the human phenylalanine hydroxylase locus using a full-length human phenylalanine hydroxylase cDNA clone as a hybridization probe to analyze human genomic DNA. These polymorphic patterns segregate in a Mendelian fashion and concordantly with the disease state in various PKU kindreds. The frequencies of the restriction site polymorphisms at the human phenylalanine hydroxylase locus among Caucasians are such that the observed heterozygosity in the population is 87.5%. Thus, most families with a history of classical phenylketonuria can take advantage of the genetic analysis for prenatal diagnosis and carrier detection of the hereditary disorder.

Reinstitution of diet therapy in PKU patients from twenty-two US clinics

In a nationwide survey we found 72 PKU (phenylketonuria) patients who had terminated diet but later returned to diet. Sixty-one patients resumed diet due to clinical problems. Age at initial diet discontinuation ranged from three to 20 years. The most prevalent problems reported were poor school performance, and mood and/or behavior changes. Following diet reinstitution, only positive changes were noted for 42 patients, no changes for 19 patients, and 11 had one or more negative changes. Improvements and blood phenylalanine levels were not significantly correlated, but only 11 patients maintained levels less than 10 mg/dl. The number of improvements was significantly correlated with length of time on diet (p less than 0.001). After a median of 10 months on diet, 22 patients had again discontinued due to poor diet control, lack of motivation, poor formula tolerance, lack of apparent benefits and/or changes for the worse. Median time on diet for the 50 second-time continuers was two years nine months.

Diet policies of PKU clinics in the United States

About two-thirds of 90 clinics treating phenylketonuria (PKU) now recommend indefinite continuation of a low phenylalanine diet as compared to 1978 when fewer than one-fourth had this policy. The percentage of children maintained on diet has increased markedly for six to eight year-olds. Greater conservatism in clinic diet recommendations likely reflects reports of adverse consequences following diet discontinuation and negative individual clinic experiences.

Cloned human phenylalanine hydroxylase gene allows prenatal diagnosis and carrier detection of classical phenylketonuria

The human gene for the hepatic enzyme phenylalanine hydroxylase has been cloned and used to analyse the phenylalanine hydroxylase locus in the human genome. The detection of polymorphisms in this locus by several restriction enzymes has allowed feasibility studies of prenatal diagnosis of classical phenylketonuria and identification of carriers of the trait. Results indicate that these services could be provided for up to 75% of all families with phenylketonuric children in the general Caucasian population.