U. von Döbeln

Phenylketonuria screening registry as a resource for population genetic studies

Background: Neonatal screening for metabolic diseases, involving samples stored on filter paper (Guthrie spots), provides a potential resource for genetic epidemiological studies. Objective: To develop a method to make these dried blood spots available for large scale genetic epidemiology. Methods: DNA from untraceable Guthrie spots was extracted using a saponin and chelex-100 based method and preamplified by improved primer preamplification. Analyses were done on 38 samples each of fresh, 10, and 25 year old Guthrie spots and the success rate determined for PCR amplification for five amplicon lengths. Results: The method was applicable even on 25 year old samples. The success rate was 100% for 100 bp amplicons and 80% for 396 bp amplicons. Ninety four Guthrie samples were genotyped, including carriers of two different PKU mutations; all carriers were found (six R158Q, four R252W), with no false positives. Finally, 2132 anonymous samples from the Swedish PKU registry were extracted and preamplified and the allele frequencies of APOε4, PPARγ Pro12Ala, and the CCR5 32 bp deletion determined. Local variations in allele frequencies suggested subpopulation structuring. There was a significant difference (p<0.01) in regional allele frequencies for the CCR5 32 bp deletion in the Swedish population. Conclusion: Whole genome amplification makes it feasible to conduct large genetic epidemiological studies using PKU screening registries.

Identification of new mutations in the ETHE1 gene in a cohort of 14 patients presenting with ethylmalonic encephalopathy

Background: Ethylmalonic encephalopathy (EE) is a rare autosomal recessive metabolic disorder characterised by progressive encephalopathy, recurrent petechiae, acrocyanosis and chronic diarrhoea, with a fatal outcome in early in life. Methods: 14 patients with EE were investigated for mutations in the ETHE1 gene. Results: Of the 14 patients, 5 were found to carry novel mutations. Conclusions: This work expands our knowledge of the causative mutations of EE.

Population structure in contemporary Sweden--a Y-chromosomal and mitochondrial DNA analysis.

A population sample representing the current Swedish population was analysed for maternally and paternally inherited markers with the aim of characterizing genetic variation and population structure. The sample set of 820 females and 883 males were extracted and amplified from Guthrie cards of all the children born in Sweden during one week in 2003. 14 Y‐chromosomal and 34 mitochondrial DNA SNPs were genotyped. The haplogroup frequencies of the counties closest to Finland, Norway, Denmark and the Saami region in the north exhibited similarities to the neighbouring populations, resulting from the formation of the Swedish nation during the past millennium. Moreover, the recent immigration waves of the 20th century are visible in haplogroup frequencies, and have led to increased diversity and divergence of the major cities. Signs of genetic drift can be detected in several counties in northern as well as in southern Sweden. With the exception of the most drifted subpopulations, the population structure in Sweden appears mostly clinal. In conclusion, our study yielded valuable information of the structure of the Swedish population, and demonstrated the usefulness of biobanks as a source of population genetic research. Our sampling strategy, nonselective on the current population rather than stratified according to ancestry, is informative for capturing the contemporary variation in the increasingly panmictic populations of the world.

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).

Severe mental retardation in 2 to 24-month-old children in Lahore, Pakistan: a prospective cohort study

Severe mental retardation (developmental quotient (DQ) < 50) was investigated in 1303 children from 2 to 24 months of age, born during 1984‐87 in four population groups representing different socioeconomic levels in and around Lahore, Pakistan. The incidence per 1000 live births was 22 in the periurban slum, 9 in the urban slum, 7 in the village and 4 in the upper middle class group. The aetiology was prenatal in 79%, perinatal in 14% and untraceable in 7% of cases. Downs syndrome was the most common cause of severe mental retardation (36%). Impairments were studied at 2 years of age. Impairment of language was present in all, while locomotor dysfunction was seen in 89% of cases. Epilepsy and cerebral palsy were each present in 22% of cases. Mortality among these severely mentally retarded children was 36%.

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.

Serum amino acid profile in patients with acute pancreatitis

Summary.Patients in the early phase of acute pancreatitis (AP) have reduced serum levels of arginine and citrulline. This may be of patho-biological importance, since arginine is the substrate for nitric oxide, which in turn is involved in normal pancreatic physiology and in the inflammatory process. Serum amino acid spectrum was measured daily for five days and after recovery six weeks later in 19 patients admitted to the hospital for acute pancreatitis. These patients had abnormal levels of most amino acids including arginine, citrulline, glutamine and glutamate. Phenylalanine and glutamate were increased, while arginine, citrulline, ornithine and glutamine were decreased compared to levels after recovery. NO2/NO3 concentration in the urine, but not serum arginase activity, was significantly increased day 1 compared to day 5 after admission. Acute pancreatitis causes a disturbance of the serum amino acid spectrum, with possible implications for the inflammatory process and organ function both in the pancreas and the gut. Supplementation of selected amino acids could possibly be of value in this severe condition.

Increased neonatal thyrotropin in Down syndrome

Aim: Down syndrome (DS) is frequently associated with thyroid dysfunction. The aim of this study was to investigate the blood concentration of thyrotropin (TSH) observed at neonatal screening of infants with DS and its possible association with development of hypothyroidism during childhood.

Increased lipolysis in LCHAD deficiency

SummaryAn increasing number of fatty acid oxidation defects are being detected owing to diagnostic improvements and a greater awareness among clinicians. The metabolic block leads to energy disruption, fatty infiltration, and toxic effects on organ functions exerted by β-oxidation metabolites. This investigation was undertaken to assess the influence of long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency on lipolysis and energy turnover. We addressed the question whether the lipolysis and glucose production rates would be altered in the fasting state in a child with this disease. Lipolysis, glucose production and resting energy expenditure (REE) were studied in a 17-month-old girl with LCHAD deficiency and her healthy twin sister. Lipolysis and glucose production were determined after a 4–6 h fast by constant-rate infusion of [1,1,2,3,3-2H5]glycerol and [6,6-2H2]glucose and analysis by gas chromatography–mass spectrometry. REE was estimated by indirect calorimetry. The affected girl showed 50% higher lipolysis than did her sister, whereas the glucose production rates were similar. Plasma levels of dicarboxylic acids of 6–12 carbon atoms chain length, 3-hydroxy fatty acids of 6–18 carbon atoms chain length, total free fatty acids, and acylcarnitines were increased in the patient, as was REE. Since glucose production rates and plasma glucose levels were similar in the two girls, the increased lipolysis observed in the patient probably represents a compensatory mechanism for energy generation. This is achieved at the price of an augmented risk for fatty acid infiltration and toxic effects of β-oxidation intermediates. This highlights the importance of avoiding fasting in these patients.

Pregnancy and lactation in a woman with classical galactosaemia heterozygous for p.Q188R and p.R333W

SummaryWe describe a 10-year-old boy with glycogen storage disease type Ib (GSD Ib) with neutropenia and neutrophil dysfunction who never suffered from severe recurrent infections. Lymphocyte subpopulations and assay of intracellular cytokines (IL-2, IL-4 and IFN-γ) showed a pattern of lymphocyte activation suggesting a shift of TH1/TH2 balance towards a TH1 response. This is the first report of GSD Ib without severe recurrent infections in spite of neutropenia and neutrophil dysfunction.