Cytogenetic profile of Down syndrome in Alexandria, Egypt

During 1992-2001, 673 Down syndrome patients were referred to the Department of Human Genetics in Alexandria. Regular [free] trisomy 21 constituted 95.4% of cases; Robertsonian translocation 2.7%; and mosaicism 0.7%. In 8 cases, regular trisomy 21 was associated with structural or numerical chromosome anomalies. Translocation was parentally inherited for 33.3% of cases and maternal transmission was twice as common as paternal. Two translocated Down syndrome fetuses were diagnosed prenatally in at [14;21] carrier mother. Mean maternal age was high in regular trisomy 21 [38.2 years] but not in translocation [25.3 years]. There was an excess of males in all groups except the mosaic group where the male:female ratio was 0.67. Cytogenetic investigations assist in patient management and family counselling

Major birth defects among infants with Down syndrome in Alexandria, Egypt [1995-2000]: trends and risk factors

We evaluated the hypothesis that the trisomy 21 genome interacts with environmental factors during early pregnancy to increase the risk for birth anomalies in Down syndrome infants in Alexandria, Egypt. A case-control study on 514 infants with confirmed Down syndrome was carried out from 1 July 1995 to 30 June 2000. Genetic, biological, environmental and reproductive factors were analysed. Multiple logistic regression analysis showed the following factors to be independently associated with increased risk of congenital heart diseases among Down syndrome patients: parental consanguinity, maternal parents' consanguinity, mother's antibiotics use in pregnancy, oral contraceptive use and diabetes in the mother. Fever in the mother during pregnancy was associated with increased risk of gastrointestinal anomalies

Nucleolus organizer region heteromorphism in patients with Down syndrome and their parents

The study aimed to evaluate the role of nucleolus organizer region [NOR] heteromorphism as an etiological factor for parental nondisjunction in Down syndrome by comparing 25 patients affected by Down syndrome, and their parents with a control group of 80 non-affected Egyptians. All parents had normal karyotypes. The average modal number per parent of Ag-positive NORs was significantly higher in parents than controls. A significant difference in the size of the double-NOR variants [dNORs] was found. The mean maternal and paternal ages were significantly lower, with a significant increase in spontaneous abortions, for dNOR[+] couples compared with dNOR[-] couples

Autosomal recessive disorders among patients attending the genetics clinic in Alexandria

A total of 660 patients referred to the genetics clinic, Medical Research Institute, Alexandria were assessed to determine the frequency of genetic disorders and the proportion of autosomal recessive disorders. It was found that 298 [45.2%] patients had genetic disorders, 100 [33.6%] of whom had an autosomal recessive disorder; these included 32 patients with metabolic defects, 18 with haemoglobinopathies and 50 with syndromes and single defects. The frequency of consanguinity among parents of patients with autosomal recessive disorders was high [60%, with 48% first cousins]. The average inbreeding coefficient was higher [0.03] than that reported for the Egyptian population in general [0.01]

Chromosomal aberrations in children with suspected genetic disorders

Karyotyping was done in 137 children suspected of having chromosomal abnormalities such as genetically uncertain syndromes, multiple congenital anomalies, short stature, dysmorphic features, unclassified mental retardation and Down syndrome. A total of 53 [38.7%] had an abnormal karyotype: trisomy 21 [36; 26.3%], trisomy 18 [3; 2.2%], trisomy 13 [1; 0.7%], partial autosomal aneuploidy [5; 3.6%], pericentric inversion of chromosome 9 [2; 1.5%], marker chromosome [2; 1.5%] and sex chromosome aberrations [4; 2.9%]. All of them showed phenotypic-cytogenetic heterogeneity. These findings suggest that cytogenetic analysis is useful in the investigation of children with genetic disorders of unknown origin to confirm clinical diagnosis and to allow for proper genetic counseling