Screening for subtle chromosomal rearrangements in an Egyptian sample of children with unexplained mental retardation

Mental retardation is present in about 1-3% of individuals in the general population, but it can be explained in about half of the cases. A descriptive study was carried out to screen for subtle chromosomal rearrangements in a group of Egyptian children with idiopathic mental retardation [IMR] to estimate its frequency if detected. The study enrolled 30 patients with IMR, with the perquisite criteria of being <18 years at referral, their IQ <70, and manifesting at least one of the criteria for selection of patients with subtelomeric abnormalities. Males were 63.3% and females were 36.7%, with a mean age of 7.08 +/- 4.22 years. Full history taking, thorough clinical examination, IQ, visual, and audiological assessment, brain CT scan, plasma aminogram, pelvi-abdominal ultrasonography, echocardiography, and cytogenetic evaluation using routine conventional karyotyping, high resolution banding [HRB], and fluorescent in situ hybridization [FISH] technique with appropriate probes were carried out for all studied patients. All enrolled patients had apparently normal karyotypes within 450 bands resolution, except for one patient who had 46, XY, [del [18] [p11.2]]. HRB and FISH showed subtle chromosomal rearrangement in 10% of cases that have been proven to be subtelomeric in 2 cases, i.e., 6.8%: 46, XY, dup [17] [p13.3], 46, XY, del [2] [q36.1-36.3], and non-subtelomeric in one case, 5.5%, 46, XX, ins [7;?] [q22;?]. To conclude, in children with IMR and clinical phenotype indicative of a suspected chromosomal anomaly, once recognizable syndromes have been excluded, abnormalities that include the ends of chromosomes must be searched for using HRB and subtelomeric FISH even when conventional karyotyping fails to demonstrate any abnormality

Genetic evaluation of non-selected group of patients with cranio facial dysmorphism

A number of congenital and acquired conditions can affect the skull, face and jaws in a wide range of craniofacial abnormalities that commonly present at birth or in early in infancy. The aim of the present study was to evaluate clinically as well as cytogenetically a non-selected group of Egyptian children with craniofacial dysmorphism whether isolated or part of the syndrome. The study included 30 patients from 28 families. Consanguinity was present in 42.8% of families and a similar affected family member was present in 6 patients [20%]. Cytogenetic analysis using high resolution karyotype was done to 24 patients. Patients were classified according to the aetiology of dysmorphism into five groups. Group 1 included patients with chromosomal abnormalities [two patients [6.7%]] and one patient with microdeletion syndrome [Rubenstein Taybi syndrome [3.3%]] which needs FISH and molecular testing for confirmation. Craniofacial dysmorphism due to monogenic disorders was present in 34.3%, multifactorial aetiology in 20%, environmental factors in 6.7%, and unknown aetiology in 20% of cases. In conclusion, the aetiology of craniofacial dysmorphism is very heterogeneous. Good observation and systematic examination can narrow the differential diagnosis and the laboratory investigations needed. High resolution karyotype is essential in all of these cases