Audiologic findings in children with biotinidase deficiency in Turkey.

OBJECTIVE: Biotinidase deficiency is an autosomal recessively inherited disorder characterized by neurological and cutaneous features, including sensorineural hearing loss. Although many features of the disorder are reversible following treatment with biotin, the hearing loss appears to be irreversible. In the present study, hearing status of patients with biotinidase deficiency is characterized in a Turkish population. METHODS: Subjective and objective audiologic tests were performed on 20 children with profound biotinidase deficiency. RESULTS: Sensorineural hearing loss occurs in approximately 55% of the children with biotinidase deficiency. The hearing loss varies in severity from mild to profound hearing loss. In children diagnosed immediately after birth because they had an older sibling with the disorder, statistically significant differences were found between ABR results and age of diagnosis (p<0.05). Greater prolongation in ABR latencies were observed in the late-diagnosed children compared to that in the early-diagnosed children (p<0.05). CONCLUSION: Early diagnosis is important to prevent peripheral and central hearing loss. Children with biotinidase deficiency who have hearing loss are likely at increased risk for having speech and language problems. If hearing aids do not provide sufficient amplification, cochlear implantation may be indicated in these children. Therefore, it is important to test the hearing thresholds of these children with hearing aids and evaluate their language development.

The effect of oral L-carnitine supplementation on the lipid profiles of hyperlipidaemic children.

AIM: To investigate the carnitine status and the effect of carnitine supplementation on serum lipid profiles in children with hyperlipoproteinaemia, a clinical open trial was conducted at Hacettepe University Ihsan Dogramaci Children's Hospital, Section of Nutrition and Metabolism. METHODS: Patients were given carnitine at a dose of 100 mg/kg/d for 12 wk. Blood samples for the determination of lipid profile and carnitine levels and urine samples for carnitine levels were obtained on admission, at week 4 and week 12 of the study period. RESULTS: A total of 41 children were enrolled in the study: 20 patients had type II heterozygotes, eight patients had type II homozygotes, three patients had type III, six patients had type V and four patients had secondary hyperlipidaemias. Serum and urine carnitine levels were within normal limits on admission. No significant correlations were found between serum carnitine levels and serum lipid profiles. Serum HDL and apolipoprotein A-I decreased significantly during the 12 wk of intervention in type II heterozygotes. In type II homozygotes, total cholesterol and LDL levels at weeks 4 and 12 increased significantly compared to initial levels. No significant change was noted for lipid parameters in hyperlipoproteinaemia type V. CONCLUSION: The results of this trial demonstrated that carnitine supplementation was of no benefit for children with hyperlipidaemias, especially in primary hyperlipoproteinaemia type II heterozygotes, homozygotes and type V.

High cystine in platelets from patients with nephropathic cystinosis: a chemical, ultrastructural, and functional evaluation.

AIM: To investigate the morphology and function of platelets in nephropathic cystinosis (NC). METHODS: Seven patients (mean age, 6.5 years; SD, 20 months) with NC were investigated. Their platelets were examined by transmission electron microscopy (TEM) and the characteristics of the dense granules (DGs) were determined by mepacrine labelling and the uranaffin reaction. Bleeding time, turbidometric aggregation, and luminescence aggregation were studied and intraplatelet cystine was measured. RESULTS: Increased intraplatelet cystine, primary and secondary aggregation defects, and the absence of ATP release were demonstrated. TEM revealed DGs of various shapes and sizes and lamellary or amorphous cytoplasmic inclusions. Viscous material had been released into the vacuolar spaces and enlarged open canalicular system. Mepacrine labelling revealed that the numbers of DGs/platelet were comparable between the patients and the controls (mean, 2.9 (SD, 0.22) v 3.32 (0.18); p = 0.34). The uranaffin reaction revealed that the numbers of type 1, 3, and 4 DGs were comparable between the patients and the controls, but that there were fewer type 2 DGs in the patients (mean, 8.5 (SD, 1.95) v 17.22 (1.58); p = 0.01). TEM for platelet aggregation revealed a lack of induction and/or defective execution and/or delayed transmission. The patients' intraplatelet cystine concentrations were higher than the controls (mean, 1.56 (SD, 0.84) v 0.08 (0.01) nmol/mg protein; p = 0.009). CONCLUSIONS: This is the first report to demonstrate raised intraplatelet cystine, abnormal platelet ultrastructural findings, and defective aggregation in NC.

Maple syrup urine disease: mutation analysis in Turkish patients.

Maple syrup urine disease (MSUD), the most frequently occurring organic acidaemia in Turkey, is caused by a deficiency of the activity of branched-chain keto acid dehydrogenase enzyme (BCKAD) complex. Mutation analysis of the E1alpha, E1beta, and E2 genes of the BCKAD complex in 12 Turkish MSUD patients yielded three disease-specific mutations and a polymorphism in the E1alpha gene, none in the E1beta gene and one mutation in the E2 gene. Among them, three missense mutations (Q80E, C213Y, T106M) and the F280F polymorphism occurring in the E1alpha gene and the splice site mutation (IVS3 - 1G>A) in the E2 gene were novel. Three of the missense mutations and the splicing mutation occurred homozygously and caused classical MSUD. One patient carried the splicing mutation homozygously and the T106M mutation in the heterozygous state; this patient is the first case having simultaneously two different mutations in two different genes in the BCKAD complex. IVS3 - IG>A splicing mutation detected on the E2 gene causes deletion of the first 14 bp of exon 3 in the mutant mRNA extending between 190 and 204 nt. The deletion spans the cleavage point between mitochondrial targeting and lipoyl-bearing site of the E2 protein.

Evaluation of a fetus at risk for dihydropteridine reductase deficiency by direct mutation analysis using denaturing gradient gel electrophoresis.

Dihydropteridine reductase (DHPR) is an enzyme involved in the recycling of tetrahydrobiopterin (BH(4)), which is an obligate co-factor of the aromatic amino acid hydroxylases. DHPR deficiency is a rare, autosomal recessive disorder caused by mutations in the QDPR gene. DHPR-deficient patients are diagnosed by a lack of response to a low phenylalanine diet and by severe neurological symptoms. Final diagnosis is made by measurements of neurotransmitters and pterin metabolites in cerebrospinal fluid (CSF) and urine, in addition to DHPR enzyme activity, which can be assessed in whole red blood cells. Treatment of DHPR deficiency can be difficult and the outcome is not always satisfying, even if all treatment strategies are followed. Therefore prenatal diagnosis is of great importance in affected families. Prenatal diagnosis is possible by measuring DHPR activity in different cell types but this is time consuming. More than 25 different mutations have to date been identified in the QDPR gene and direct identification of a mutation in a fetus would be easy and rapid. We have developed a method based on denaturing gradient gel electrophoresis (DGGE) for the analysis of the QDPR gene. The method is useful for rapid and simultaneous scanning of all exons and flanking intronic sequences of the QDPR gene. We describe the first prenatal diagnosis conducted using this method.

Factor V Leiden mutation in Turkish patients with homozygous cystathionine beta-synthase deficiency.

Venous and arterial thromboembolism can occur in patients with homocystinuria. Resistance to activated protein C, which is caused by a single point mutation in the gene for factor V, renders an individual at risk for thrombosis. It has been suggested that coexistence of hereditary homocystinuria and factor V Leiden mutation might jointly play a role in the development of thrombosis. We analysed six patients with homocystinuria due to cystathionine beta-synthase deficiency for factor V Leiden and prothrombin G20210A mutations. Only one patient was found to have the factor V Leiden mutation in homozygous form and this patient had suffered from severe thrombosis. One patient was found to be heterozygous with no documented thrombosis. None of the patients had prothrombin G20210A mutation. We stress the necessity for screening for known thrombophilic risk factors in patients with cystathonine beta-synthase deficiency. The coexistence of the factor V Leiden mutation can cause severe thrombotic events in patients with homocystinuria.

Molecular genetic analyses of cystinuria type 1 in 24 Turkish patients.

M467T mutation (exon 8) in rBAT gene is found to be the most common mutation in cystinuria type I patients. In our series consisting of 24 patients, the allele frequency of the M467T mutation was 8.3 percent (4/48). The second most frequent mutation at the same nucleotide position was M467K, with an allele frequency of 4.2 percent (2/48). The polymorphism which is found in linkage disequilibrium with the M467T is 231T/A (exon 1). We also found that 231T/A was associated with the M467T mutation in our series.

Newborn PKU screening in Turkey: at present and organization for future.

At present, pkenylketonuria screening is a national child health program in Turkey which is carried out collaboratively by the Ministry of Health and three University Children's Hospitals in Ankara, Istanbul and Izmir. Since 1986 the number of cities included in the screening program has gradually increased, now and it covers all the metropolises the country. A total of 383 babies were found with persistent hyperphenylalaninemia (1:4,172) among 1,605,582 babies screened by the Guthrie test at the Hacettepe Screening Center in Ankara. By taking into account pretreatment phenylalanine levels and phenlyalanine tolerances at five years of age, the numbers of classical and mild-moderate phenylketonuria and mild hyperphenylalaninemia cases were 216, 102 and 58, respectively. The major problems encountered in the screening program and in management of the detected cases were unsatisfactory sample collection, early discharge from maternity hospitals, difficulties in reaching some detected cases, and noncompliance with dietary therapy due to illiterate parents or to lack of social insurance. To screen and treat all newborns for phenylketonuria and to include at least hypothyroidism in the screening program, there is a need for a more disciplinary intersectoral approach than exists at present.

Mutation analysis in Turkish patients with hereditary fructose intolerance.

Thirteen Turkish patients with hereditary fructose intolerance (HFI) were screened for the three common mutations, A149P, A174D and N334K, in the aldolase B gene that have been detected frequently in European population. We found that nine of the patients carry the A149P mutation in both alleles, which corresponds to a frequency of about 55%. Single-strand conformation analysis of all coding exons of the gene was also performed to detect unknown mutations in four patients not carrying the three common mutations. No aberrant migration patterns were observed in these patients.

Molecular analysis of 16 Turkish families with DHPR deficiency using denaturing gradient gel electrophoresis (DGGE).

Dihydropteridine reductase (DHPR) catalyses the conversion of quinonoid dihydrobiopterin (qBH2) to tetrahydrobiopterin (BH4), which serves as the obligatory cofactor for the aromatic amino acid hydroxylases. DHPR deficiency, caused by mutations in the QDPR gene, results in hyperphenylalaninemia and deficiency of various neurotransmitters in the central nervous system, with severe neurological symptoms as a consequence. We have studied, at the clinical and molecular levels, 17 patients belonging to 16 Turkish families with DHPR deficiency. The patients were detected at neonatal screening for hyperphenylalaninemia or upon the development of neurological symptoms. To identify the disease causing molecular defects, we developed a sensitive screening method that rapidly scans the entire open reading frame and all splice sites of the QDPR gene. This method combines PCR amplification and "GC-clamping" of each of the seven exonic regions of QDPR, resolution of mutations by denaturing gradient gel electrophoresis (DGGE), and identification of mutations by direct sequence analysis. A total of ten different mutations were identified, of which three are known (G23D, Y150C, R221X) and the remaining are novel (G17R, G18D, W35fs, Q66R, W90X, S97fs and G149R). Six of these mutations are missense variants, two are nonsense mutations, and two are frameshift mutations. All patients had homoallelic genotypes, which allowed the establishment of genotype-phenotype associations. Our findings suggest that DGGE is a fast and efficient method for detection of mutations in the QDPR gene, which may be useful for confirmatory DNA-based diagnosis, genetic counselling and prenatal diagnosis in DHPR deficiency.

Neurological crisis mimicking acute pancreatitis in tyrosinemia type I.

Hereditary tyrosinemia results from an inborn error in the final step of tyrosine metabolism. Neurological manifestations have been reported in nearly half of patients during illness to have characteristics of altered consciousness, weakness, anorexia, vomiting, and pain in the extremities and abdomen. His physical findings and laboratory results pointed out acute pancreatitis. There have been some reports of acute and chronic pancreatitis in patients with metabolic diseases; however, this is the first case with tyrosinemia type I who exhibited clinical and biochemical findings of acute pancreatitis during neurological crisis. The presented case suggests the possibility that the pancreas is affected in neurological crisis. The determination of amylase concentration both in serum and urine samples of further cases will clarity the association between pancreatitis and neurological crisis.