Maternal hyperphenylalaninemias in healthy Czech population of pregnant women: 30 years experience with screening, prevention and treatment.

INTRODUCTION: The increased level of phenylalanine (Phe) in maternal blood--hyperphenylalaninemia (mHPA) has a detrimental effect on the early development of healthy foetus (1965). The toxic effect causes spontaneous abortion or retards intrauterine growth, skeletal malformation, cardiac anomalies can appear. However the most frequent are microcephaly, mental retardation and hypotrophy. PATIENTS AND METHODS: Simultaneously with the introduction of obligatory "Newborn Screening Program" in CR also the facultative screening for mHPA was introduced ("Maternal Hyperphenylalaninemia Preventive Screening Program"). Since 1975 till now 222,990 healthy pregnant women (16-47 yrs) from city Prague and its area (cca 2 mil. inh.) have been screened for increased Phe in blood by Efron's chromatographic screening test (1964); Phe cut off value: 240 micromol/l. Nonfasting venous blood has been taken in 2nd-3rd month of pregnancy during the first antenatal visit. All positive cases have been verified with quantitative Phe estimation on amino acid analyzer incl. pterines analysis in urine. For differentiation of detected mHPAs the Güttler's scheme (1980) has been used. Mutations for Phe-hydroxylase gene analyzed by restriction enzyme digestion after Guldberg (1994). RESULTS: The average incidence of mHPA detected at the beginning of pregnancy was found 1:8675. The major part (65.3%) of all detected mHPA belongs to mild or moderate form of phenylketonuria (PKU) with most frequent PAH gene mutations R408W, Y414C, IVS11 nt8g-a, R158Q, IVS12ntlg-a and R261Q. 19.2% corresponds to atypical or classical PKU with prevailing mutation R408W. Only in 15.3% were detected non-PKU (persistent HPA) with mutations R408W, Y414C, IVS12ntlg-a, IV11nt8g-a and A403V. 28 offsprings born from pregnancies on low-phenylalanine diet (LPD) introduced at least 2 months before the conception and during the whole pregnancy show normal psychomotoric development. In 7 offsprings without LPD or after delayed introducing or on PLD or badly monitored showed malformations (microcephaly, hypotrophy, skeletal malformations) or died. DISCUSSION: Relatively high incidence of mHPA detected in healthy population of pregnant women of Prague area differs from findings of Buist (1989) or Levy (1994) from American pregnant women screened for mHPA from umbilical blood. We consider that screening performed at the beginning of pregnancy from nonfasting venous blood is more effective compared to umbilical blood from two reasons: the Phe level in maternal blood is increased during first trimester of pregnancy due to succing effect of placenta in comparison to decreased Phe level at the end of labour. Umbilical blood for screening of mHPA is not quite suitable to detect the atypical or mild forms of Phe disturbances which prevailed in our Slavonic population of pregnant women. (Tab. 5, Fig. 7, Ref. 16.)

[Maternal hyperphenylalaninemia in a population of healty Czech women. 18 years' experience with mass screening, diet therapy and metabolic monitoring]. / Materské hyperfenylalaninémie v ceské populaci zdravých tehotných zen. 18leté zkusenosti s fakultativním screeningem, dietní lécbou a metabolickým sledováním.

BACKGROUND: Elevated phenylalanine levels in maternal blood (hyperphenylalaninaemia) during pregnancy damages the developing foetal tissues. Early detection of pregnant women with hyperphenylalaninaemia and adherence to a low phenylalanine diet already before conception and throughout pregnancy can prevent this damage. The objective of the investigation are results achieved screening and strict monitoring of low phenylalanine dietetic treatment in detected pregnant women of the Prague population. METHODS AND RESULTS: 186 350 healthy women of the Prague population were examined by the chromatographic screening test in a venous blood sample during their first visit in a maternity welfare centre and 22 positive cases were detected (incidence 1:8470). In 86% mild, persistent or benign forms of phenylketonuria were involved. Nineteen patients were treated by a low phenylalanine diet and the phenylalanine tolerance was monitored as well as the nitrogen balance, amino acids in serum and urine, protein markers, trace elements, vitamins, lipids, the body mass index-BMI, changes of body weight after introduction of the dietetic treatment and treatment during pregnancy. A significant increase of the phenylalanine tolerance by 20 to 200% was found, mostly in the second half of pregnancy and reduced values of serum and urinary selenium. The decrease of body weight when the diet was introduced and the increment during pregnancy correlated with the BMI value. In the other investigated parameters no significant deviations were found. CONCLUSION: Fifteen healthy children with normal psychomotor development delivered by 12 mothers with hyperphenylalaninaemia provide evidence of the effectiveness of prenatal screening for hyperphenylalaninaemia during pregnancy.

A ten-year follow-up study of urinary screening for inherited metabolic disorders.

Urine samples of 200,000 sucklings in 6th-8th month after delivery was analyzed by means of chromatographic screening test for amino acids, sugars and muccopolysacharides. In 1.4% of them persistent and in 51.6% transitory hyperaminoacidurias, in 0.15% persistent and 12.5% transitory melliturias and in 0.05% alcaptonuria were detected. No one case of muccopolysacharidosis was detected. 239 persistent metabolic disorders were detected. These disorders were not possible to detect by means of an obligatory screening test performed on 5th-6th day after delivery from capillary blood. All positive detected cases were verified by detailed metabolic investigation (thin layer, liquid and gas-chromatography).

Results of screening for phenylalanine and other amino acid disturbances among pregnant women.

Blood specimens were collected from 15000 pregnant women during the first 3 months of their pregnancy and screened for amino acid disturbances by means of paper chromatography. A high incidence of disturbances in the phenylalanine metabolism was discovered: three cases of mild hyperphenylalaninaemia without phenylpyruvicaciduria (incidence 1:5000); two cases of mild hyperphenylalaninaemia with phenylpyruvicaciduria (incidence 1:7550); four cases of mild phenylketonuria (incidence 1:3750). Disturbances in the metabolism of other amino acids were found to be rare. Metabolic and genealogical findings in some detected families are briefly described.

Results of phenylalanine tolerance tests and EEG examination in patients under treatment for phenylketonuria.

The EEG of 10 phenylketonuric children treated by a diet and of 4 children with hyperphenylalaninaemia on a normal diet was recorded during L-phenylalanine tolerance tests. The first recording was made before administering the L-phenylalanine load (100 mg/kg b.w.) and the second 60-120 min after. In 6 of the phenylketonuric children, nonspecific abnormality became more pronounced or increased, or previously absent epileptic graphoelements appeared. A pathological EEG response to a L-phenylalanine load was found in 1 child with hyperphenylalaninaemia. The authors do not recommend relaxation of the diet in children with a pathological EEG response to a L-phenylalanine load.

Hyperglycinaemia without ketosis.

When screening mentally backward children we detected a 5-year-old child with elevated urinary glycine excretion and a high blood glycine level. The report discusses the results of a clinical, metabolic and genetic examination of the child and the members of his family with reference to this rare metabolic disorder.