الفهرس 
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Abstract
Congenital heart disease (CHD) refers to structural heart defects, which impair the cardiac function. It is the most common disorder among live births with an incidence of 10/1,000 newborns. It is also considered a major cause of morbidity and mortality, especially when associated with extra cardiac malformations.
CHD in combination with other malformations occurs in about 25% of the cases, many of them being part of a pattern of specific defects or genetic syndromes. Down syndrome and Velocardiofacial syndrome are the most commonly seen in patients with CHD. In most CHD patients, the cause is multifactorial, including environmental teratogens and genetic or chromosomal conditions. Maternal illnesses play a significant role in the development of heart defects in fetuses. Although the embryo does not have the disease, prolonged exposure to metabolites of the maternal illness leads to the development of congenital malformations.
Despite the strong genetic basis, a specific genetic etiology is identified in about 20% of CHD cases. This reflects the need for high accuracy screening tests for detecting causative genetic alterations.
Recent reports have shown that recurrent copy number variants (CNVs) may be found in 20% of patients with CHD. Multiplex ligation-dependent probe amplification (MLPA) is an established, cost-effective and relatively simple technique for detection of known CNVs. MLPA assay specifically designed for screening of CHD patients could be used as a first-tier screening assay.
Recently, the application of chromosomal microarray analysis (CMA) for clinical diagnosis allowed the identification of submicroscopic genomic imbalances across the genome that could not be detected by routine karyotyping or FISH analysis. However, the use of whole genome techniques is laborious and very costly.
In the present study an attempt was made to shed light on the probable role of some prevalent environmental factors in children with Congenital heart disease (CHD) complicated with other somatic features and to introduce Multiplex Ligation Dependent Probe Amplification (MLPA) technique as a screening tool for detection of genomic imbalances among them.
The present study was conducted on 40 children with congenital heart defects associated with extracardiac malformations and/or developmental delay or intellectual disability with an age spectrum ranging from newborns to teenagers.
All patients were subjected to complete history taking including interview risk factor questionnaire, pedigree analysis and thorough clinical examination. Conventional cytogenetic analysis and MLPA were done for all patients using SALSA MLPA probe mix P245-B1 Microdeletion syndromes and SALSA MLPA Probe mix P070-B3 Sub telomeres Mix 2B.5. CMA was done for one patient with characteristic dysmorphic features showing negative results by MLPA.
All the studied patients showed normal karyotypes. By using MLPA five patients (12.5%) showed chromosomal microdeletions. [2 patients (5%) showed 7q11.23 deletion (Williams’s syndrome), 1 patient (2.5%) showed 4p16.3 deletion (Wolf-Hirschhorn syndrome) and 1 patient (2.5%) showed 22q11.2 deletion (Digeorge syndrome)]. One patient (2.5%) showed 2p25.3 subtelomere duplication. CMA performed for patient No. 6 showed an interstitial 2.27 Mb deletion of chromosome 2q22 including the entire ZEB2 gene causing Mowat Wilson syndrome.
William syndrome patients (number 1 and 2) suffered from supravalvular aortic stenosis, cardiomegaly, facial dysmorphism and patient number one suffered also from mild MR. William syndrome is mainly due to ELN gene deletion located in region 7q11.23.
Patient (3) diagnosed with Wolf-Hirschhorn syndrome showing typical deletion in 4p16.3, presented with intellectual disability and CHD associated with microcephaly, short stature, dysmorphic facial features and agenesis of the corpus callosum.
Patient (4) showed 2p25.3 sub telomere duplication and presented with VSD, global developmental delay (GDD), dysmorphic facies and tonic convulsions.
Patient (5) suffered from CHDs, delayed milestones, microcephaly and dysmorphic facial features characteristic of 22q11.2 deletion syndrome also known as DiGeorge syndrome, MLPA analysis confirmed the diagnosis showing the typical deletion in 22q11.2 region encompassing the TBX1 gene seen in 22q11.2 deletion syndrome.
Patient (6) had respiratory distress, cyanosis, CHD, delayed milestones. His clinical examination revealed microcephaly, peculiar dysmorphic facies. His neurological examination revealed agenesis of the corpus callosum and. CMA showed an interstitial 2.27 Mb deletion of chromosome 2q22 encompassing ZEB2 gene causing Mowat Wilson syndrome. The most common molecular defects seen in Mowat-Wilson syndrome patients are de novo heterozygous pathogenic abnormalities in the ZEB2 gene including deletions and mutations.
Conventional karyotyping is only efficient in detecting changes larger than 5-10 Mb, which is present in nearly 9% of the CHD cases.. Recently, the advances in microarrays technologies increased the rate of detection of chromosomal aberrations in patients with CHD to nearly 16.6-30%.The array methodology is now used as the first tier test for screening of newborn presenting with CHD mainly due to its high diagnostic rate. However, the array methodology is has a relatively high cost making its wide-scale usage in developing countries limited. The introduction of Multiplex Ligation dependent
Probe Amplification (MLPA) technique was considered a good feasible alternative genetic test with a relatively good cost-benefit ratio for CHD patients. The use of MLPA analysis in our study increased the diagnostic yield to reach about 12.5%.
Till now, the investigations of the etiology of CHD are advanced on two major ways; environmental and genetic. Environmental risk factor assessment revealed maternal history of fever or infections in 47.5% with flu occurring in 42.5% and taking drugs in 37.5%, mostly antipyretic and antibiotics in few cases. It also showed that 67.5% of females were overweight with 25% of them being obese. As regards to children delivery circumstances 22.5% were born with asphyxia and cyanosis.
Regarding paternal characteristic risk factors 33% of the fathers gave history of occupational exposures to building materials, insecticides, heat & and noise, fumes and & detergents. Thirty percent of fathers and 15% of mothers gave a history of chronic diseases mostly in the form of hypertension and type 2 diabetes. Fathers were cigarettes and shisha smokers by 62.5% and 12.5% respectively, while only two mothers smoked cigarettes and only one smoked shisha.
The incorporation of both environmental and genetic factors in large analytical studies can improve our understanding of their main effects and about genetic environmental interactions, which can help us more in the field of the genetic pathophysiology of CHD. This can improve prevention strategies through better diagnostic testing which may allow early efficient intervention, targeted therapeutic procedures, and appropriate family counseling.