No abstract

Introduction: Clinical variability associated with the common 22q11.2 microdeletion is well known, and has led to a broad application of FISH diagnostics with probes for loci TUPLE1 or D22S75 (N25), although, rarely reported atypical deletions associated with the same phenotypic spectrum would not be discovered by these probes. As most types of 22q11.2 deletions occur between low copy repeats within the region (LCR22), we assumed that atypical deletions should be more common than has been reported. To address this question and the possibility of a deletion size related genotype-phenotype correlation, we systematically assessed the frequency of typical and atypical 22q11.2 deletions in a large cohort of patients. Methods: We used a set of 10 fluorescent in situ hybridisation (FISH) DNA probes, capable of detecting all reported and hypothetical deletions between the LCR22, and analysed 350 patients. Deletion sizes in atypical deletions were established by use of further FISH probes. Frequency of certain atypical deletions was analysed in controls by FISH and quantitative PCR. Results: Patients with conotruncal heart defects (ctCHD) and with typical VCFS phenotype showed the common 3 Mb or nested 1.5 Mb deletions (in 18.5% and 78.6%, respectively), but no atypical deletion, while 5% (3/63) of patients with a mildly suggestive, atypical phenotype showed atypical distal deletions, which were not detected in patients with mental retardation of unknown origin or in healthy controls. Discussion: These statistically significant differences demonstrate that atypical distal 22q11.2 deletions are very uncommon in patients with ctCHDs, while atypical congenital heart defects and mild dysmorphism are recognisable feature of atypical distal deletions. Further phenotype-genotype analysis disclosed association of significant developmental delay with the distal part of the common deletion region, and choanal atresia and atypical CHDs with the adjacent distal deletion region.

2 Structured abstractBackground: Tetralogy of Fallot (TOF), the most frequent cyanotic congenital heart disease, is associated with a wide range of intra-and extracardiac phenotypes. In order to get further insight into genotype-phenotype correlation we comprehensively investigated a large cohort of 230 unselected patients with TOF. Methods and Results:We studied 230 patients with TOF by karyotyping, comprehensive 22q11.2 deletion testing and sequencing of TBX1, NKX2.5 and JAG1, as well as molecular karyotyping in selected patients. We found pathogenic genetic aberrations in 42 patients (18%), with 22q11.2 deletion as the most common diagnosis (7.4%), followed by trisomy 21 (5.2%) and other chromosomal aberrations or submicroscopic copy number changes (3%). Mutations in JAG1 were detected in three patients with Alagille syndrome (1.3%), while NKX2.5 mutations were seen in two patients with non-syndromic TOF (0.9%). One patient showed a recurrent polyalanine stretch elongation within TBX1 for which we show that this represents a true mutation resulting in loss of transcriptional activity due to cytoplasmatic protein aggregation. Conclusion: We show that 22q11.2 deletion represents the most common known cause of TOF and that the associated cardiac phenotype is distinct for obstruction of the proximal pulmonary artery, hypoplastic central pulmonary arteries and subclavian artery anomalies. Atrioventricular septal defect associated with TOF is very suggestive of trisomy 21 and almost excludes 22q11.2 deletion. We report a further patient with a recurrent polyalanine stretch elongation within TBX1 and for the first time link TBX1 cytoplasmatic protein aggregation to congenital heart defects.3 Abstract Tetralogy of Fallot (TOF), the most frequent cyanotic congenital heart disease, is associated with a wide range of intra-and extracardiac phenotypes. We investigated genotype-phenotype correlation in a large cohort of 230 unselected patients with TOF, in whom we performed karyotyping, comprehensive 22q11.2 deletion testing and sequencing of TBX1, NKX2.5 and JAG1, as well as molecular karyotyping in patients with TOF and otherwise unexplained mental retardation. We found pathogenic genetic aberrations in 42 patients (18%), with 22q11.2 deletion as the most common diagnosis (7.4%), followed by trisomy 21 (5.2%) and other chromosomal aberrations or submicroscopic copy number changes (3%). Mutations in JAG1 were detected in three patients with Alagille syndrome (1.3%), while NKX2.5 mutations were seen in two patients with non-syndromic TOF (0.9%). One patient showed a polyalanine stretch elongation within TBX1 which was previously reported as variant of unknown significance in a patient with isolated interruption of the aortic arch. We show that this represents a true mutation resulting in loss of transcriptional activity due to cytoplasmatic protein aggregation, for the first time linking the latter to congenital heart defects. The cardiac anomalies of this patient fit into the spectrum of 22q11.2 deletion, and were distin...

A prophylactic anticoagulation strategy that considers the surgical technique and potential predisposing circumstances proved effective in the prevention of late thrombotic complications after total cavopulmonary anastomosis. There is no need for routine anticoagulation during long-term follow-up after Fontan-type surgery in pediatric patients.