الفهرس 
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Abstract
In the general population, congenital heart diseases are the most common of all congenital birth defects. They are caused by improper development and may produce symptoms at birth, during childhood and sometimes not until adulthood. About 0.5-0.8% of all children are born with congenital heart diseases (at about 8-10 out of every 1000 children every year). 5% or more of cardiovascular anomalies have no currently known cause .However; it appears to result from an interaction between multifactorial genetic and environmental factors. The 22q11 microdeletion was first described in 1968 as a primary Immunodeficiency resulting form the abnormal development of structures arising from the third and fourth pharyngeal pouches during embryonic life. Its incidence is 1:4000 live births. It is caused by the deletion of a small piece of chromosome 22 (microdeletion). Originally, a deletion of 1.5-3.0 megabases was described. Newer genetic techniques have refined the deletion breakpoints, and identified intragenic point mutations in TBX-1. In addition, modifier genes are considered to contribute to the highly variable phenotype. The main aim of this study is to detect the incidence of 22q11.2 deletion syndrome among children with isolated congenital heart lesions.
The present study was carried on 20 children. Their ages ranged from 30 days to 24 months. The study included 5 males and 15 females. All subjects were chosen from those admitted in the cardiology unit of the pediatric department of Tanta University Hospital.
All patients were subjected to: full history taking, complete clinical and laboratory examination, radiological examination including chest x-ray and echocardiography, cytogenetic study to detect 22q1.2 deletion using fluorescent in situ hybridization (FISH) technique.
The study revealed the presence of 22q11.2 deletion among 2 out of 20 children having isolated congenital heart lesions included in the study.
The higest incidence was among the cases of patent ductus arteriosus(PDA) 1/5,followed by ventricular septal defect (VSD)1/9.None of the cases having tetralogy of fallot (TOF)had the deletion.
It is clear from this study that infants with congenital heart disease, especially of conotroncus origin, should be tested for 22q11.2 chromosomal deletion. This fact is even more relevant if one takes into account the potential benefit of preventive measures that could be applied if such diagnosis were defined. This will also provide early management and follow up to conditions that are usually associated with the syndrome such as hypocalcaemia and immunodeficiency which should be suspected when such syndrome is diagnosed.
However, molecular diagnosis of 22q11.2 deletion is not widely available; it is of great importance, therefore, to make methodologies available that could guarantee screening of a large number of individuals at tertiary care hospitals.
In conclusion, 22q11DS is a relatively common abnormality among patients with congenital heart disease. Variations between studies seem to be associated mainly with the selection process and characteristics of the population . Identification of these patients is essential for their adequate management and genetic counseling.
Form our results we concluded that 22q11 microdeletion should be suspected in patients with isolated heart lesions whether associated with extracardiac features such as craniofacial dysmorphism and developmental delay or not and hence FISH study to detect the deletion should be considered in such patients.