L. Hagenfeldt

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency: Newborn screening and its relationship to the diagnosis and treatment of the disorder

Abstract Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency can be detected by newborn screening. The screening alone in 29 programs from 13 countries resulted in the diagnosis of CAH in 1 2 of affected newborns and expedited the diagnosis in 1 3 of affected newborns clinically suspected to have CAH. The benefits of newborn screening for CAH were prevention of severe adrenal crisis, its sequela, incorrect male sex assignment of severely virilized female newborns, and progressive signs of androgen excess. Screening revealed a higher incidence of CAH worldwide (1:15000 live births) compared with the case survey incidence (1:32000 live births) The false-positive rate (usually found in low birth weight and premature infants) was acceptably low (0.01–0.5%) except for three programs (0.7–2.5%). The false-negative rate of CAH screening was negligible. Prenatal diagnosis of CAH is possible by HLA typing or 21-hydroxylase B gene analysis of cultured fetal cells from chorionic villus biopsy sampling in the first trimester and from amniotic cells or hormonal analysis of amniotic fluid in the second trimester. Prenatal treatment of CAH is possible via maternal dexamethasone therapy beginning early pregnancy. However, efficacy and side effects of maternal dexamethasone therapy require further investigation.

Relation between genotype and phenotype in Swedish phenylketonuria and hyperphenylalaninemia patients

Phenylketonuria (PKU) and hyperphenylalaninemia (HPA) are caused mostly by an inherited (autosomal recessive) deficiency in hepatic phenylalanine hydroxylase (PAH) activity. More than 50 PAH mutations have ben reported. The goal of the present study was to examine the molecular basis for the clinical heterogeneity of Swedish PKU and HPA patients. Mutations were identified through allele-specific oligonucleotide hybridization or DNA sequencing on 128 of the 176 mutant alleles (73%). Three mutations (R408W, Y414C and IVS12) together accounted for 56% of all mutant alleles and ten relatively infrequent mutations were found on another 17% of all mutant alleles. Patients from 50 of the 88 families (57%) had identified mutations in both PAH genes and allowed use to compare the clinical effects of different combinations of PAH mutations. The in vitro activity of all of these mutations, including the newly identified G272X and ΔL364, have been tested in a eukaryotic expression system. There was a strong relationship between the average in vitro PAH activity of the two mutant enzymes and both the phenylalanine tolerance and the neonatal pretreatment serum phenylalanine concentration. This confirms previous observations in Danish and German PKU patients that disease phenotype is a consequence of the nature of the mutations at the PAH locus and not significantly influenced by other loci. The sample population in the previous study did not, however, include mild HPA patients, and the observed correlation is thus restricted to severe and moderate mutant alleles. Since a comparatively high proportion of the Swedish patients were mildly affected, we have provided additional evidence that this correlation is valid throughout a continuous spectrum of clinical varieties. PAH genotyping could therefore help predict prognosis of a recently diagnosed PKU or HPA child.

Clinical and biochemical presentation of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency

Interest in inherited defects in the later steps of mitochondrial ]~-oxidation started with the observation of patients with a 3-hydroxydicarboxylic aciduria (Pollitt et al 1987; Hagenfeldt et al 1990). Most of these patients were later shown to be deficient in the long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) activity. Meanwhile, investigations of this enzyme activity in human liver showed that it resides in a trifunctional protein that also harbours enoyl-CoA hydratase and 3-oxoacyl-CoA thiolase activities (Carpenter et al 1992). It has recently been demonstrated that many patients with LCHAD deficiency also have a decrease in one or both of the other two activities of the trifunctional protein (Kamijo et al 1994; Venizelos et al 1994).

Neonatal Screening for Congenital Adrenal Hyperplasia Using 17-Hydroxyprogesterone Assay in Filter Paper Blood Spots

Screening of infants for congenital adrenal hyperplasia (CAH) using filter paper blood samples collected on the 5th day of life was performed with a radioimmunoassay for 17-hydroxyprogesterone without extraction with organic solvents. A total of 153,000 newborns were screened and 12 cases of CAH were detected (1:12,800). With recall levels related to gestational age, the recall rate could be lowered to 0.05%.

Fatty acid oxidation in fibroblasts from patients with defects in β-oxidation and in the respiratory chain

Fatty acid oxidation has been studied with the tritium release assay in cultured fibroblasts from patients with defects in β-oxidation and in the mitochondrial respiratory chain. Cells from all patients with β-oxidation defects and cells from 10 of 16 patients with respiratory chain defects showed an impairment of fatty acid oxidation. The result of the tritium release assay is not only dependent on the proper function of the β-oxidation cycle but is also influenced by the reoxidation of reduced cofactors. The assay can thus be used to study the expression of respiratory chain defects in cultured fibroblasts.

Screening of half a million Swedish newborn infants for congenital adrenal hyperplasia

Abstract Using filter paper blood samples, 557,000 newborn infants were screened for congenital adrenal hyperplasia (CAH). 17-Hydroxyprogesterone was determined by radioimmunoassay without organic solvent extraction. By the use of gestational age-related cut-off limits the false positive rate could be decreased to less than 0.03% (1:4000). Two thirds of the false-positive cases were preterm infants, with a mean gestational age of 28 weeks (range 24–36 weeks). The prevalence of CAH in the screened population was 1:11,600, which does not differ from the figure obtained before the start of screening. The sensitivity of the screening test was 0.92 and the predictive value of a positive screening test was 0.24. The screening result was available at the age of 11 days (median). By screening it was possible 1.0 avoid serious salt loss after the age of 2 weeks. Screening resulted in earlier diagnosis in at least 50% of all cases of CAH. It also led to earlier correct gender assignment in virilized girls. The cost of screening was approximately 2.6 US

Fatal neonatal lactic acidosis with respiratory insufficiency due to complex I and IV deficiency.

per infant (or 32,000 US

Prevalence of the 985A»G mutation in the medium-chain acyl-CoA dehydrogenase (MCAD) gene in Sweden

per CAH patient). We conclude that the benefits of screening are significant, and suggest that CAH screening should be included in the routine neonatal screening program in Sweden.

NEONATAL SCREENING FOR CONGENITAL ADRENAL HYPERPLASIA (CAH) USING 17-HYDROXYPROGESTERONE (17-OHP) ASSAYS OF DRIED BLOOD SPOTS

We present a newborn boy who died after 53 days of life in respiratory failure with lactic acidosis. Analysis of skeletal muscle mitochondria dcmonstraled a combined defcct in complexes 1 and IV of the respiratory chain. The boy had severe muscle hypotonia but no signs of encephalopathy, illustrating the variation in multi‐organ prescntation of mitochondrial defects.

Mitochondrial function in neuroleptic-free and medicated schizophrenia

The prevalence of the 985A>G mutation in the medium-chain acyl-CoA dehydrogenase gene was determined in the Swedish population. A heterozygote frequency of 1:127 was observed. Morbidity data indicate that most of the homozygotes with this mutation are not diagnosed and probably remain asymptomatic.