Résumé
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
Sujets)
Adulte , Femelle , Humains , Mâle , Épidémiologie moléculaire , Fréquence d'allèle , Conseil génétique , Hôpitaux universitaires , Nouveau-né , Caryotypage , Âge maternel , Mosaïcisme/statistiques et données numériques , Orientation vers un spécialiste/statistiques et données numériquesRésumé
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