[Show abstract][Hide abstract] ABSTRACT: Noninvasive prenatal testing (NIPT) validation studies show high sensitivity and specificity for detection of trisomies 13, 18, and 21. False negative cases have rarely been reported. We describe a false negative case of trisomy 13 and another of trisomy 18 in which NIPT was commercially marketed directly to the clinician. Both cases came to our attention because a fetal anatomy scan at 20 weeks of gestation revealed multiple anomalies. Karyotyping of cultured amniocytes showed nonmosaic trisomies 13 and 18, respectively. Cytogenetic investigation of cytotrophoblast cells from multiple placental biopsies showed a low proportion of nontrisomic cells in each case, but this was considered too small for explaining the false negative NIPT result. The discordant results also could not be explained by early gestational age, elevated maternal weight, a vanishing twin, or suboptimal storage or transport of samples. The root cause of the discrepancies could, therefore, not be identified. The couples involved experienced difficulties in accepting the unexpected and late-adverse outcome of their pregnancy. We recommend that all parties involved in caring for couples who choose NIPT should collaborate to clarify false negative results in order to unravel possible biological causes and to improve the process of patient care from initial counseling to communication of the result.
[Show abstract][Hide abstract] ABSTRACT: Therapy for mild haemophilia A consists of desmopressin acetate (1-deamino[8-D arginine]-vasopressin, desmopressin, DDAVP) which increases FVIII and von Willebrand factor antigen (VWF:Ag) levels two to six fold through endogenous release from endothelial cells (1). The effect of desmopressin varies between patients and is suggested to depend on the haemophilia causing mutation (2-4). Mild haemophilia is generally caused by F8 missense mutations. One of these mutations is c.1910A>G, p.Asn637Ser. In our haemophilia treatment center (the Van Creveldkliniek, University Medical Center Utrecht,The Netherlands), a large cohort of patients with this particular mutation is known. To investigate the variability in increase of FVIII after desmopressin infusion in this cohort of patients, a retrospective single centre study was performed. This article is protected by copyright. All rights reserved
[Show abstract][Hide abstract] ABSTRACT: Primary immunodeficiency (PID) disorders are a heterogeneous group of inherited disorders caused by a variety of monogenetic immune defects. Thus far, mutations in more than 170 different genes causing PIDs have been described. A clear genotype-phenotype correlation is often not available, which makes a genetic diagnosis in patients with PIDs complex and laborious.
We sought to develop a robust, time-effective, and cost-effective diagnostic method to facilitate a genetic diagnosis in any of 170 known PID-related genes by using next-generation sequencing (NGS).
We used both targeted array-based and in-solution enrichment combined with a SOLiD sequencing platform and a bioinformatic pipeline developed in house to analyze genetic changes in the DNA of 41 patients with PIDs with known mutations and 26 patients with undiagnosed PIDs.
This novel NGS-based method accurately detected point mutations (sensitivity and specificity >99% in covered regions) and exonic deletions (100% sensitivity and specificity). For the 170 genes of interest, the DNA coverage was greater than 20× in 90% to 95%. Nine PID-related genes proved not eligible for evaluation by using this NGS-based method because of inadequate coverage. The NGS method allowed us to make a genetic diagnosis in 4 of 26 patients who lacked a genetic diagnosis despite routine functional and genetic testing. Three of these patients proved to have an atypical presentation of previously described PIDs.
This novel NGS tool facilitates accurate simultaneous detection of mutations in 161 of 170 known PID-related genes. In addition, these analyses will generate more insight into genotype-phenotype correlations for the different PID disorders.
The Journal of allergy and clinical immunology 10/2013; 133(2). DOI:10.1016/j.jaci.2013.08.032 · 11.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The development of neutralizing antibodies against factor VIII (FVIII) is a major complication of treatment with FVIII in patients with severe haemophilia A. This study was designed to describe the relationship between the type and location of the factor 8 (F8) gene mutation and the development of clinically relevant inhibitors in patients with severe haemophilia A. We conducted a single centre cohort study among 318 consecutive patients (baseline FVIII activity level <0.01 IU mL(-1)) born between 1934 and 2007 who were treated with FVIII on at least 50 exposure days. The primary outcome was clinically relevant inhibitor development, defined as the occurrence of at least two positive inhibitor titres and a decreased recovery. Clinically relevant inhibitors were diagnosed in 14% (43) of patients (30 high-titre). The cumulative incidence of inhibitor development was 18% (35 of 200) in high-risk gene defects (67% in patients with large deletions, 30% in patients with nonsense mutations, 15% in patients with intron 1 or 22 inversions) and 7% (8 of 118) in low-risk gene defects (7% in patients with small deletions and insertions, 6% in patients with missense mutations, 8% in patients with splice site mutations). In patients with point mutations, the cumulative risk of developing inhibitors was highest in patients with mutations in the A3 and C2 domains (13% and 17% respectively). In conclusion, in agreement with earlier observations, the type and location of the F8 gene mutation were important determinants of inhibitor development in patients with severe haemophilia A.
[Show abstract][Hide abstract] ABSTRACT: Juvenile polyposis (JP) and hereditary hemorrhagic telangiectasia (HHT) are clinically distinct diseases caused by mutations in SMAD4 and BMPR1A (for JP) and endoglin and ALK1 (for HHT). Recently, a combined syndrome of JP-HHT was described that is also caused by mutations in SMAD4. Although both JP and JP-HHT are caused by SMAD4 mutations, a possible genotype:phenotype correlation was noted as all of the SMAD4 mutations in the JP-HHT patients were clustered in the COOH-terminal MH2 domain of the protein. If valid, this correlation would provide a molecular explanation for the phenotypic differences, as well as a pre-symptomatic diagnostic test to distinguish patients at risk for the overlapping but different clinical features of the disorders. In this study, we collected 19 new JP-HHT patients from which we identified 15 additional SMAD4 mutations. We also reviewed the literature for other reports of JP patients with HHT symptoms with confirmed SMAD4 mutations. Our combined results show that although the SMAD4 mutations in JP-HHT patients do show a tendency to cluster in the MH2 domain, mutations in other parts of the gene also cause the combined syndrome. Thus, any mutation in SMAD4 can cause JP-HHT. Any JP patient with a SMAD4 mutation is, therefore, at risk for the visceral manifestations of HHT and any HHT patient with SMAD4 mutation is at risk for early onset gastrointestinal cancer. In conclusion, a patient who tests positive for any SMAD4 mutation must be considered at risk for the combined syndrome of JP-HHT and monitored accordingly.
American Journal of Medical Genetics Part A 02/2010; 152A(2):333-9. DOI:10.1002/ajmg.a.33206 · 2.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Familial mediterranean fever (FMF) is a hereditary autoinflammatory autosomal recessive disease caused by mutations in the MEFV gene. Despite the identification of many disease associated MEFV mutations, often the clinical diagnosis cannot be genetically confirmed. The currently used diagnostic sequencing techniques only allow the detection of point mutations, small deletions or duplications. The question as to whether larger genetic alterations are also involved in the pathophysiology of FMF remains to be answered. To address this question, we used multiplex ligation-dependent probe amplification (MLPA) on a total of 216 patients with FMF symptoms. This careful analysis revealed that not a single deletion/duplication could be detected in this large cohort of patients. This result suggests that single or multiexon MEFV gene copy number changes do not contribute substantially, if at all, to the MEFV mutation spectrum.
European Journal of HumanGenetics 11/2008; 16(11):1404-6. DOI:10.1038/ejhg.2008.135 · 4.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We encountered a homozygous -16C>G mutation in cis at identical positions in the promoters of both human gamma-globin genes in a subject who was also homozygous for Hemoglobin C (HbC). Subsequent analysis of normal control individuals of African American ancestry revealed that both mutations were always present in cis with an allelic frequency of 3%. Furthermore, 10 out of 11 HbC subjects carried the -16C>G sequence variations, suggesting an association with HbC. The -16C>G mutation disrupts a putative CACCC box positioned between the TATA box and the transcriptional start site. However, the absence of high levels of HbF in HbC subjects homozygous and heterozygous for the -16C>G sequence variation suggested no effect of this mutation on gamma-globin gene expression in the adult stage of development. Further functional characterization by means of transient transfections in human erythroleukemic K562 cells showed that the -16C>G promoter sequence variation did not have an effect on gamma-globin expression in the fetal stage of development either. We therefore conclude that the -16C>G gamma-globin sequence variations are not beneficial to the clinical phenotype of HbC. The unique concurrent presence of this non-functional sequence variation is likely the result of a gene conversion event, and supports the concept of sequence homogenization between the two human gamma-globin genes.
[Show abstract][Hide abstract] ABSTRACT: Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disease exhibiting multifocal vascular telangiectases and arteriovenous malformations. The majority of cases are caused by mutations in either the endoglin (ENG) or activin receptor-like kinase 1 (ALK1, ACVRL1) genes; both members of the transforming growth factor (TGF)-beta pathway. Mutations in SMAD4, another TGF-beta pathway member, are seen in patients with the combined syndrome of juvenile polyposis (JP) and HHT (JP-HHT).
We sought to determine if HHT patients without any apparent history of JP, who were undergoing routine diagnostic testing, would have mutations in SMAD4. We tested 30 unrelated HHT patients, all of whom had been referred for DNA based testing for HHT and were found to be negative for mutations in ENG and ALK1.
Three of these people harboured mutations in SMAD4, a rate of 10% (3/30). The SMAD4 mutations were similar to those found in other patients with the JP-HHT syndrome.
The identification of SMAD4 mutations in HHT patients without prior diagnosis of JP has significant and immediate clinical implications, as these people are likely to be at risk of having JP-HHT with the associated increased risk of gastrointestinal cancer. We propose that routine DNA based testing for HHT should include SMAD4 for samples in which mutations in neither ENG nor ALK1 are identified. HHT patients with SMAD4 mutations should be screened for colonic and gastric polyps associated with JP.
Journal of Medical Genetics 11/2006; 43(10):793-7. DOI:10.1136/jmg.2006.041517 · 5.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterised by vascular malformations in multiple organ systems, resulting in mucocutaneous telangiectases and arteriovenous malformations predominantly in the lungs (pulmonary arteriovenous malformation; PAVM), brain (cerebral arteriovenous malformation; CAVM), and liver (hepatic arteriovenous malformation; HAVM). Mutations in the ENG and ALK-1 genes lead to HHT1 and HHT2 respectively. In this study, a genotype-phenotype analysis was performed. A uniform and well classified large group of HHT patients and their family members were screened for HHT manifestations. Groups of patients with a clinically confirmed diagnosis and/or genetically established diagnosis (HHT1 or HHT2) were compared. The frequency of PAVM, CAVM, HAVM, and gastrointestinal telangiectases were determined to establish the genotype-phenotype relationship. The analysis revealed differences between HHT1 and HHT2 and within HHT1 and HHT2 between men and women. PAVMs and CAVMs occur more often in HHT1, whereas HAVMs are more frequent in HHT2. Furthermore, there is a higher prevalence of PAVM in women compared with men in HHT1. In HHT1 and HHT2, there is a higher frequency of HAVM in women. HHT1 has a distinct, more severe phenotype than HHT2. There is a difference in the presence of symptoms between men and women. With these data, genetic counselling can be given more accurately when the family mutation is known.
Journal of Medical Genetics 05/2006; 43(4):371-7. DOI:10.1136/jmg.2005.035451 · 5.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease is an autosomal dominant disorder characterized by an aberrant vascular development. The resulting vascular lesions range from smaller mucocutaneous telangiectases to large visceral arteriovenous malformations, especially in the skin, lung, gastrointestinal tract and the brain. Mutations in the genes encoding endoglin (ENG, chromosome 9q34) and activin A receptor type-like kinase 1 (ALK-1, also named ACVRL1, chromosome 12q13) are associated with HHT1 and HHT2, respectively. We report here on the genetic and molecular heterogeneity found in the HHT population in the Netherlands. Probands of 104 apparently unrelated families were studied and we performed sequence analysis on both the ENG gene and ALK-1 gene. In most of the probands, we found a mutation in one of the two genes: 53% in the ENG gene and 40% in the ALK-1 gene. In 7% of the families no ENG or ALK1 mutation was found. The mutations detected were deletions, insertions, nonsense, missense and splice site mutations. The majority were novel mutations.
Human Genetics 02/2005; 116(1-2):8-16. DOI:10.1007/s00439-004-1196-5 · 4.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Wilson disease is an hereditary disorder of copper metabolism, caused by mutations in the ATP7B gene, and leading to hepatic or neurologic disease. We examined whether H1069Q, the most common ATP7B mutation, is associated with a specific phenotype.
Genotyping results in 70 Dutch patients were related to clinical presentation. Subsequently a meta-analysis for genotype-phenotype correlation was performed on all patients available from literature, combined with the current Dutch group, a total of 577 patients.
The Dutch patients homozygous or heterozygous for the H1069Q mutation presented more frequently with neurologic disease (63% and 43% vs. 15%), and at a later age (20.9 and 15.9 vs. 12.6 years) than patients without the H1069Q mutation. In the meta-analysis the odds-ratio for neurologic presentation in homozygous or heterozygous H1069Q vs. non-H1069Q patients was 3.50 (95% CI 2.01-6.09) and 2.13 (95% CI 1.18-3.83), respectively. Age at presentation was 21.1, 19.2 and 16.5 years, respectively, corresponding to a weighted mean difference (WMD) of 4.41 (95% CI 1.56-7.26) for homozygous H1069Q vs. heterozygous patients and 6.68 (95% CI 4.33-9.38) for homozygous H1069Q vs. non-H1069Q patients.
Our results indicate that the H1069Q mutation is associated with a late and neurologic presentation.
Journal of Hepatology 12/2004; 41(5):758-63. DOI:10.1016/j.jhep.2004.07.017 · 10.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Four unrelated patients with glyceroluria ranging from 7 to 170 mmol/l were studied. The activity of glycerol kinase (GK) in cultured fibroblasts was determined with a specific enzyme assay and with two indirect methods, that is, incorporation into macromolecules of [(14)C] from [(14)C]glycerol and its oxidation to [(14)C]CO(2). Exon amplification and RT-PCR were used to identify mutations. In patient 1, with low activity in all three assays, we identified a c.1194A>C (E398D) missense mutation. In patient 2 with a considerable activity of the GK enzyme (22% of reference), oxidation to [(14)C]CO(2) (37%) and a high incorporation of [(14)C] into macromolecules (92%), we identified a c.182T>C (L61P) mutation that causes the enzyme to have a higher K(m) for glycerol ( approximately 300 microM) than normals (2-8 microM). In patient 3, the GK activity estimated by the three different methods ranged from 16 to 22% of reference. Analysis of mRNA from the GK gene revealed three alternatively spliced transcripts. A mutation in intron 3 (g.16835G>A) resulted in an insertion of a cryptic exon between exon 2 or 3 and exon 4. Patient 4 with minor glyceroluria (7 mmol/l) and normal plasma glycerol concentration had normal activity with all three assay methods, thus excluding GK deficiency (GKD) as a cause of slight glyceroluria. To evaluate fully patients with glyceroluria, one needs to measure the GK activity and relate this and the clinical data to genetic findings. Residual enzyme activities in cultured fibroblasts can be found in GKD patients with severe clinical symptoms.
European Journal of HumanGenetics 06/2004; 12(6):424-32. DOI:10.1038/sj.ejhg.5201172 · 4.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To evaluate at what gestational age fetal DNA can reliably be detected at the earliest in maternal plasma.
We performed consecutive blood sampling in the first trimester of pregnancy in 17 women who were pregnant after in vitro fertilization (IVF) or intrauterine insemination (IUI). DNA was isolated and the Y-chromosome specific SRY was amplified by real-time polymerase chain reaction (PCR). We likewise studied 31 women prior to invasive prenatal diagnosis procedures for test validation purposes. All test results were compared to cytogenetic sex or sex at birth.
The earliest SRY detection was at a gestational age of 5 weeks and 2 days. In none of 4 pregnancies ending in a miscarriage was SRY detected. We detected SRY in maternal plasma in 1 of 2 patients (50%) carrying a male fetus at a gestational age of 5 weeks, in 4 of 5 (80%) at a gestational age of 7 weeks, in 4 of 4 (100%) at a gestational age of 9 weeks. In all 7 women pregnant with a male fetus, the correct fetal sex was detected by 10 weeks. In none of the 6 patients who delivered a girl was SRY detected. In the validation group, SRY was detected in 13 of the 13 male, and none of the 18 female fetuses.
We conclude that real-time PCR of the SRY gene promises to be a reliable technique for early fetal sexing in maternal plasma.
[Show abstract][Hide abstract] ABSTRACT: Wilson disease is an autosomal recessive disorder of copper metabolism. The gene defective in Wilson disease encodes a copper transporting P-type ATPase expressed in the liver. The disturbed export of copper into bile results in accumulation of copper in liver and secondarily in other organs such as the brain. These patients generally present with either hepatic or neurological symptoms.
Nederlands tijdschrift voor geneeskunde 04/2003; 147(13):603-5.
[Show abstract][Hide abstract] ABSTRACT: Pyruvate kinase (PK) deficiency is a common cause of hereditary non-spherocytic haemolytic anaemia. It is an autosomal recessive disorder caused by mutations in the gene coding for erythrocyte and liver-type pyruvate kinase (PKLR). So far, more than 130 mutations in this gene have been identified. Clinical symptoms, usually restricted to homozygous and compound-heterozygous individuals, are variable, ranging from neonatal jaundice requiring erythrocyte transfusions to a fully compensated haemolytic anaemia. The exact mechanism of erythrocyte destruction is unknown, however adenosine-triphosphate depletion and an increase in 2,3-disphosphoglycerate are thought to be important. The diagnosis of pyruvate kinase deficiency depends upon the demonstration of low PK enzyme activity. Due to the pitfalls in determining true PK activity, DNA testing is a valuable tool in the diagnosis of pyruvate kinase deficiency. By centralizing the molecular diagnostics of pyruvate kinase deficiency in Utrecht, more care can be provided for the diagnosis, treatment and support of patients.
Nederlands tijdschrift voor geneeskunde 10/2002; 146(39):1828-31.
[Show abstract][Hide abstract] ABSTRACT: Autosomal dominant cerebellar ataxias (ADCAs), or spinocerebellar ataxias (SCAs), are a heterogeneous group of neurodegenerative disorders. Mild CAG repeat expansions in the alpha(1A) voltage-dependent calcium channel gene are associated with SCA type 6 (SCA6).
To obtain further insight into the contribution of SCA6 mutations to the phenotypic variability in Dutch patients with ataxia.
Survey and case series.
Hospitalized care, referral center.
The SCA6 locus was analyzed for CAG repeat expansions in a referred sample of 220 Dutch families with progressive cerebellar ataxia. Clinical characteristics of patients with SCA6 were investigated and correlated with molecular findings.
The diagnosis SCA6 was confirmed in 24 families comprising 30 familial and 4 sporadic cases. Mean +/- SD age at onset was 50.1 +/- 11.1 years. Expanded CAG repeats with sizes 22, 23, and 25 were found. These sizes correlated inversely with age at onset. No intergenerational changes in CAG repeat size were detected. Despite this, 2 families showed clinical anticipation.
This study provides the first detailed description of Dutch patients with SCA6. Clinical analysis identifies SCA6 as a late-onset ataxia in which eye movement abnormalities are prominent and consistent early manifestations. No single clinical sign can be considered specific for SCA6. Some patients have ataxia combined with episodic headaches or nausea, suggesting an overlap among SCA6, eposidic ataxia type 2, and familial hemiplegic migraine. Spinocerebellar ataxia type 6 accounts for approximately 11% of all Dutch families with ADCA. Analysis of SCA6 contributes further to the genetic classification of patients with ADCA, including patients without a clear family history of the disease.