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

Glutathione peroxidase enzyme and selenium level in patients with Down syndrome

In recent years, it has been hypothesized that an increase in oxidative stress in patients with Down syndrome account for the appearance of different diseases such as atherosclerosis, accelerated cell aging, cellular mutagenicity and neurological disorders that often occur in these patients. The antioxidant defense system enzymes have been shown to be altered due to increased gene dosage on chromosome 21 and overproducetion of superoxide dismutase. The purpose of this study was to investigate the activity of glutathione peroxidase enzyme [GPX] and the level of selenium [Se] as indicators of antioxidative metabolism in Down syndrome patients. The study was conducted on forty patients with Down syndrome. They were 21 males and19 females. Their ages ranged between 1 year and 11 years [mean 3.95 +/- 2.5 years]. Another group was randomly chosen as a control group, it included 10 normal infants and children, 5 males and 5 females. Their ages ranged between 1 year and 11 years [mean 3.95 +/- 4.47 years]. All cases and controls were subjected to plasma glutathione peroxidase enzyme assay and plasma selenium level determination. There was a significant increase in GPX activity in Down syndrome patients compared to the control group. There was no statistical significant difference between cases and controls as regards selenium level. In Down syndrome group, there was no significant difference in GPX and selenium levels between males and females and between different age groups. There was a significant negative correlation between GPX activity and Se level in Down syndrome patients. Down syndrome patients have increased activity of glutathione peroxidase enzyme and although they have normal plasma Se level, there is a significant negative correlation between selenium level and GPX activity. This finding suggests that the selenium requirement of the enzyme is not met and there is a relative selenium deficiency