Maternal phenylketonuria: report from the United Kingdom Registry 1978-97.

BACKGROUND: The effects of maternal phenylalanine on the fetus include facial dysmorphism, microcephaly, intrauterine growth retardation, developmental delay, and congenital heart disease. AIMS: To evaluate the impact of phenylalanine restricted diet in pregnant women with phenylketonuria (PKU) on their offspring. METHODS: Data on virtually all pregnancies of women with PKU in the United Kingdom between 1978 and 1997 were reported to the United Kingdom PKU Registry. The effect of the use and timing in relation to pregnancy of a phenylalanine restricted diet on birth weight, birth head circumference, the presence or absence of congenital heart disease (CHD), 4 year developmental quotient, and 8 year intelligence quotient were examined. RESULTS: A total of 228 pregnancies resulted in live births (seven twin pregnancies were excluded). In 110 (50%), diet started before conception. For this group mean (SD) birth weight was 3160 (612) g, birth head circumference 33.6 (1.9) cm, 4 year DQ 108.9 (13.2), 8 year IQ 103.4 (15.6), and incidence of CHD was 2.4%. In comparison, for those born where treatment was started during pregnancy (n = 91), birth weight was 2818 (711) g, birth head circumference 32.7 (2.0) cm, 4 year DQ 96.8 (15.0), 8 year IQ 86.5 (13.0), and incidence of CHD was 17%. Month-by-month regression analyses suggested that metabolic control by 12-16 weeks gestation had most influence on outcome. CONCLUSIONS: Many features of the maternal PKU syndrome are preventable by starting a phenylalanine restricted diet. Women with PKU and their carers must be aware of the risks and should start the diet before conception, or as soon after as possible.

Maternal and umbilical cord erythrocyte omega-3 and omega-6 fatty acids and haemorheology in singleton and twin pregnancies.

BACKGROUND: Being devoid of both nuclei and mitochondria, mature human erythrocytes provide an opportunity to study membrane structure and function outwith the restrictions of genetic control. With its unique rapid increase in vascularisation, pregnancy is considered the most opportune period in which to investigate blood rheology. METHODS: Maternal and fetal (cord) bloods were retained at delivery from 32 (25 singleton and seven twin) normal pregnancies at two maternity hospitals in the Glasgow area over a nine month period. Erythrocyte fatty acid compositions were assessed by mass spectroscopy, and corresponding membrane deformabilities measured by ultrafiltration through a membrane of 5 micro m diameter pore size, to mimic placental microcirculation. RESULTS: Significant direct correlations (Spearman rank) were found between erythrocyte membrane omega-3 docosahexaenoic acid concentrations and corresponding deformabilities in maternal and cord blood from both singleton and twin pregnancies, whereas greater omega-6 arachidonic acid content was associated with increased maternal membrane rigidity. Membrane concentrations of omega-3 fatty acids only correlated strongly both within and between maternal and cord bloods. Mean cord erythrocyte docosahexaenoic acid concentration was higher than maternal in singletons but lower in twins. When maternal erythrocyte concentrations exceeded about 7% (of total fatty acids), resistance to erythrocyte flow was virtually eliminated. CONCLUSIONS: It may be that a greater maternal intake of docosahexaenoic acid should be encouraged in some pregnancies for optimal tissue perfusion. Fetal demand for docosahexaenoic acid may not be entirely satisfied in multiple pregnancies.

Infant cerebellar gray and white matter fatty acids in relation to age and diet.

There is little evidence as to the fatty acid composition of the cerebellum in infancy and it remains uncertain whether milk diet can influence its composition. We therefore examined cerebellar gray and white matter of infants less than 6 month old who had died unexpectedly. The fatty acid content of 33 gray and 21 white matter specimens from infants born at term and 6 gray and 5 white matter specimens from preterm infants was assessed by gas chromatographic/mass spectrometric analysis. Infants were grouped according to whether they had received human or manufactured formula milk. Whereas cerebellar cortex docosahexaenoic acid (DHA, 22:6n-3) concentrations were significantly lower (P<0.01) in the formula-fed than breast-fed infants, no differences existed between the term (n = 10) and preterm (n = 5) Synthetic Milk Adapted [corrected] (SMA) formula-fed infants. Cerebellar white matter DHA concentrations were similarly lower (P<0.01) in the SMA formula-fed infants (n = 8) than in an age-matched breast-fed group. Low concentrations of cerebellar white matter lignoceric (24:0) and nervonic acid (24:1n-9) in two 7-wk-old preterm infants appeared to correlate with postgestational rather than chronological age. Dietary long-chain polyunsaturated fatty acids, particularly DHA, are probably essential for normal development of the infant cerebellum.

Infant growth and aorta total lipid fatty acids.

Abnormal fetal and infant growth have increasingly been correlated with adult onset cardiovascular disease. To date, there is little known about the lipid fatty acid profiles in infant cardiovascular tissue. Therefore, we analysed total lipid fatty acids from thoracic and abdominal aorta intima and media from 24 normally grown sudden infant death syndrome cases. Aorta from small for gestational age (n = 2), failure to thrive from birth (n = 3), and premature (n = 1) infants were also examined. Dihomo-gamma-linolenic acid (C20:3n-6) and oleic acid (C18:1n-9) concentrations were significantly lower in the thoracic than in the abdominal aorta. Similar dietary related differences were found in the subgroup (n = 15) of infants fed on formula milks. Both abdominal and thoracic intimal arachidonic (C20:4n-6) to dihomo-gamma-linolenic acid ratios were greater in the infants with retarded growth after birth than in their normally grown counterparts. Growth restriction in infancy might disrupt the normal accretion of vascular endothelial polyunsaturated fatty acids.

Neuropsychological outcome of experimental manipulation of phenylalanine intake in treated phenylketonuria.

Blood phenylalanine concentrations were experimentally increased for 3 months by means of a phenylalanine-complemented amino acid supplement in a group of 16 children aged 10-16 years with classical phenylketonuria who had been treated early and who had remained on the restricted diet. Average concentrations achieved during challenge were between 1000 and 1300 mumol/L. Psychological outcome was measured by a neuropsychological battery consisting of tests of verbal and spatial memory, attention and fine motor coordination. A triple-blind, repeated measures, randomized, crossover design was adopted to control for practice and expectancy effects. Subjects were assessed at baseline and at the end of the first and second phenylalanine manipulation periods. Significant interactions (ANOVA) emerged as predicted for phenylalanine concentrations, but similar crossover effects were not found for any of the neuropsychological tests. The results suggested that medium-term hyperphenylalaninaemia in treated PKU is not harmful to psychological functioning in older children and adolescents who have been continuously treated up to and beyond age 10 years, though the susceptibility of executive functions needs to be further researched. The findings add some weight to the idea that by late childhood the vulnerability of the nervous system to the neurotoxic influence of phenylalanine may be much reduced.

Sequence variation at the phenylalanine hydroxylase gene in the British Isles.

Using mutation and haplotype analysis, we have examined the phenylalanine hydroxylase gene in the phenylketonuria populations of four geographical areas of the British Isles: the west of Scotland, southern Wales, and southwestern and southeastern England. The enormous genetic diversity of this locus within the British Isles is demonstrated in the large number of different mutations characterized and in the variety of genetic backgrounds on which individual mutations are found. Allele frequencies of the more common mutations exhibited significant nonrandom distribution in a north/south differentiation. Differences between the west of Scotland and southwestern England may be related to different events in the recent and past histories of their respective populations. Similarities between southern Wales and southeastern England are likely to reflect the heterogeneity that is seen in and around two large capital cities. Finally, comparison with more recently colonized areas of the world corroborates the genealogical origin by range expansion of several mutations.

Newborn screening for inborn errors of metabolism: a systematic review.

OBJECTIVES. To establish a database of literature and other evidence on neonatal screening programmes and technologies for inborn errors of metabolism. To undertake a systematic review of the data as a basis for evaluation of newborn screening for inborn errors of metabolism. To prepare an objective summary of the evidence on the appropriateness and need for various existing and possible neonatal screening programmes for inborn errors of metabolism in relation to the natural history of these diseases. To identify gaps in existing knowledge and make recommendations for required primary research. To make recommendations for the future development and organisation of neonatal screening for inborn errors of metabolism in the UK. HOW THE RESEARCH WAS CONDUCTED. There were three parts to the research. A systematic review of the literature on inborn errors of metabolism, neonatal screening programmes, new technologies for screening and economic factors. Inclusion and exclusion criteria were applied, and a working database of relevant papers was established. All selected papers were read by two or three experts and were critically appraised using a standard format. Seven criteria for a screening programme, based on the principles formulated by Wilson and Jungner (WHO, 1968), were used to summarise the evidence. These were as follows. Clinically and biochemically well-defined disorder. Known incidence in populations relevant to the UK. Disorder associated with significant morbidity or mortality. Effective treatment available. Period before onset during which intervention improves outcome. Ethical, safe, simple and robust screening test. Cost-effectiveness of screening. A questionnaire which was sent to all newborn screening laboratories in the UK. Site visits to assess new methodologies for newborn screening. The classical definition of an inborn error of metabolism was used (i.e., a monogenic disease resulting in deficient activity in a single enzyme in a pathway of intermediary metabolism). RESEARCH FINDINGS. INBORN ERRORS OF METABOLISM. Phenylketonuria (PKU) (incidence 1:12,000) fulfilled all the screening criteria and could be used as the 'gold standard' against which to review other disorders despite significant variation in methodologies, sample collection and timing of screening and inadequacies in the infrastructure for notification and continued care of identified patients. Of the many disorders of organic acid and fatty acid metabolism, a case can only be made for the introduction of newborn screening for glutaric aciduria type 1 (GA1; estimated incidence 1:40,000) and medium-chain acyl CoA dehydrogenase (MCAD) deficiency (estimated incidence 1:8000-1:15,000). Therapeutic advances for GA1 offer prevention of neurological damage but further investigation is required into the costs and benefits of screening for this disorder. MCAD deficiency is simply and cheaply treatable, preventing possible early death and neurological handicap. Neonatal screening for these diseases is dependent upon the introduction of tandem mass spectrometry (tandem MS). This screening could however also simultaneously detect some other commonly-encountered disorders of organic acid metabolism with a collective incidence of 1:15,000.(ABSTRACT TRUNCATED)

What is core? Guidelines for the core curriculum in paediatrics.

A key point that the UK General Medical Council addressed in its recommendations on the undergraduate medical education was the concept of 'core curriculum' (General Medical Council 1993). Although enthusiastic for the idea of reducing factual overload, many medical teachers found themselves facing the task of how to define what a core curriculum is, what should be included and why. Predictably, our initial response is to include common and important topics, but how common is common, and how does one determine the relative importance of topics? We do not claim to have unravelled all the ambiguities surrounding the subject nor to have resolved all the controversies that are inevitably encountered. We hope, however, to describe some of the principles that governed our approach and put forward some guidelines, that may contribute to the debate.

Recommendations for protein and amino acid intake in phenylketonuric patients.

The methods for the determination of protein requirements are reviewed and the difficulties in achieving the recommendations of the dietary management of phenylketonuria proposed by a Medical Research Council Working Party on Phenylketonuria using currently available low phenylalanine (Phe) protein substitutes and low protein foods are examined. These recommendations are that all infants whose blood Phe concentrations exceed 600 mumol/l in the presence of a normal or low plasma tyrosine and an otherwise normal plasma amino acid profile while receiving a normal protein intake (2-3 g/kg/day), should start a low Phe diet immediately. Infants whose blood Phe concentrations remain persistently between 400 and 600 mumol/l for more than a few days should also start treatment. The diet should contain a protein substitute which is Phe free (or at least very low in Phe) and otherwise nutritionally complete with a composition sufficient to provide 100-120 mg/kg per day of tyrosine and a total amino acid intake of at least 3 g/kg per day in children under 2 years of age. In children over 2 years the intake of amino acids should be maintained at a level of 2 g/kg per day. The protein substitute should be spread as evenly as possible through the 24 h. Blood Phe concentrations should be maintained between 120 and 360 mumol/l. In children aged over 10 years it is suggested that the protein substitute should supply the protein reference nutrient intake + 50%. An upper blood Phe limit of 480 mumol/l rather than 360 mumol/l may be acceptable in school age children. Adults and adolescents should continue treatment with the aim to maintain blood Phe concentrations no higher than 700 mumol/l. During the period before conception and during pregnancy women should aim to have plasma Phe concentrations between 60-250 mumol/l.

Discordant phenylketonuria phenotypes in one family: the relationship between genotype and clinical outcome is a function of multiple effects.

Four members spanning three generations of one family have phenylketonuria of varying degrees of severity. Two first cousins were screened in the neonatal period and have had dietary phenylalanine restriction since diagnosis, the older patient having been classified as having more severe PKU and the younger one as having mild PKU. Their mutual grandfather and his older brother also have a significant hyperphenylalaninaemia and are of normal intelligence despite never having had restricted phenylalanine intake. Mutation analysis of the phenylalanine hydroxylase (PAH) gene has established that there are four different mutations, two in exon 2 (F39L and L48S) and two in exon 3 (R111X and S67P), which give rise to PKU in this family. In order to establish their relative severity, we screened the PKU populations of western Scotland and the south west of England for these mutations. The exon 3 mutations are rare; however, F39L is relatively common in Scotland and L48S in England. A comparison of diagnostic blood phenylalanine concentrations in subjects carrying L48S/null or F39L/null mutations with those carrying two null mutations suggest that these exon 2 mutations are less deleterious. Thus, in this family, the different biochemical phenotypes can be explained, in part, by different genotypes at the PAH locus but our results show that the relationship between genotype and clinical outcome is more complex and is a function of multiple effects.

Age- and dietary-related distributions of hepatic arachidonic and docosahexaenoic acid in early infancy.

A dietary-related deficiency of docosahexaenoic acid [C22:6(n-3)] in infant cerebral cortex has been identified. Absence or very low rates of hepatic synthesis from the essential fatty acid precursor, alpha-linolenic acid [C18:3(n-3)], in early life may have been a contributory factor. We have analyzed liver total lipid fatty acid compositions in 27 term (37-42 wk gestation) and 4 preterm (30-33 wk gestation) infants who died within the first 6 mo of life from sudden infant death syndrome. The infants were fed exclusively either human or formula milks. Formula-fed infants were subdivided into two groups, one receiving SMA milk with an alpha-linolenic acid content at 1.5% of total fatty acids and the other a composite group fed milks with low alpha-linolenic acid concentrations (< 0.1% to 0.4%). The hepatic content of arachidonic acid [C20:4(n-6)] and docosahexaenoic acid was generally lower in both formula-fed groups than in the human milk-fed group. The age-related distributions of docosahexaenoic acid showed that coincident minimum levels were present in both formula groups in the third month of life. This may indicate that the hepatic enzymes involved in the final stage (delta 4-desaturation) conversion of alpha-linolenic acid to docosahexaenoic acid could be inactive in the first months of life. Emphasis must be on provision of preformed dietary docosahexaenoic acid and possibly arachidonic acid as well as their essential fatty acid precursors, to both term and preterm infants for at least the first 16 wk of life.

Effect of diet on the fatty acid composition of the major phospholipids of infant cerebral cortex.

The fatty acid compositions of the major cerebral cortex phospholipids, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine were measured in 16 term and one preterm 'cot death' infants fed exclusively either breast milk or one of two formulas. Docosahexaenoic acid (DHA; C22:6n-3) content in cerebral cortex phosphatidylethanolamine and phosphatidylserine of breast fed infants was greater than in both formula groups with significances varying between p < 0.1 and p < 0.001. Compensation for this deficiency in DHA in the formula fed infants was largely achieved by increased incorporation of docosapentaenoic acid (C22:5n-6) in the cerebral cortex of term infants and Mead (C20:3n-9) and dihomo Mead acids (C22:3n-9) in the preterm infant. As the phospholipids most affected are known to perform an important role in membrane function and are possibly integral to neurotransmission it is recommended that breast milk substitute infant formulas should contain n-3 and n-6 series polyunsaturated fatty acids in proportions similar to those of human milk.

Mutation analysis of the phenylalanine hydroxylase gene using heteroduplex analysis with synthetic DNA constructs.

Using heteroduplex analysis generated with synthetic PCR-amplifiable DNA we have screened the PKU populations of southwest England and Wales, western Scotland, and southeast and central England for mutations in exons 3, 7 and 12 of the phenylalanine hydroxylase (PAH) gene. The technique characterized three mutations in exon 12, two in exon 3 and five in exon 7. Altogether over 370 PKU chromosomes were screened. In all geographical regions exon 12 mutations (R408W, IVS12nt1g- > a and Y414C) accounted for about 40% of mutant chromosomes. Exon 3 mutations (principally I65T) were found on between 9 and 12% of mutant alleles and exon 7 mutations accounted for a further 5-7%. Heteroduplex analysis is rapid, simple and safe and three constructs covering three exons can identify between 55 and 60% of mutations in various PKU populations of the UK.

Artificial ultraviolet whole-body radiation does not modify serum lipoprotein, plasma fibrinogen, plasminogen or antithrombin III concentrations in post-myocardial infarction patients.

The relationship of ischaemic heart disease (IHD) to seasonal and latitude variation has prompted speculation that exposure to the ultraviolet component of solar radiation may reduce IHD risk. This hypothesis was partially tested by exposing 14 post-myocardial infarction patients to a 6 week course of artificial whole-body ultraviolet radiation (UVR). Serum lipoprotein and plasma coagulation factor concentrations were measured before and after the course of UVR. Results were compared with similar measurements from a placebo-controlled group of 13 post-myocardial patients. Despite a more than two-fold rise in mean serum 25-OHD, serum lipoprotein and plasma fibrinogen, antithrombin III and plasminogen concentrations did not change significantly in the UVR group. Significant but minor change in prothrombin time and thrombin time in the placebo group appear unlikely to be of biological significance. Seasonal and latitude variation in these IHD risk factors appear unrelated to corresponding variation in solar UVR exposure.

Breast feeding in Scotland.

OBJECTIVE: To measure the prevalence of breast feeding and to examine the value of using information collected on Guthrie cards (used for detecting inherited metabolic disease and hypothyroidism when newborn infants are 7 days old) to calculate this prevalence. DESIGN: Analysis, by geographical area and maternity unit, of information on breast feeding collected on Guthrie cards for 131,759 babies born in 1990 and 1991, and comparison with prevalences from other sources. SETTING: Scotland. RESULTS: Of the 131,759 babies, only 46,949 (35.6%) were breast feeding on day 7. The prevalence of breast feeding ranged from 59.1% (376/636) in Shetland to 21.1% (1836/8719) in Lanarkshire and < 8% in some postcode districts of cities. Analysis of the data by hospital of birth showed that the prevalence ranged from 51.2% (2701/5275) to 16.4% (507/3090). CONCLUSION: The prevalence of breast feeding in Scotland is low and varies among areas and maternity units. Intervention to increase this prevalence is essential, and information collected on Guthrie cards is a useful indication of mothers' intentions to breast feed.