ABSTRACT
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 a t(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.
Subject(s)
Cytogenetics , Down Syndrome/epidemiology , Down Syndrome/genetics , Adult , Cytogenetics/methods , Down Syndrome/prevention & control , Egypt/epidemiology , Female , Gene Frequency , Genetic Counseling , Hospitals, University , Humans , Infant, Newborn , Karyotyping , Male , Maternal Age , Molecular Epidemiology , Mosaicism/statistics & numerical data , Paternal Age , Pedigree , Referral and Consultation/statistics & numerical data , Retrospective Studies , Risk Factors , Sex Distribution , Translocation, Genetic/geneticsABSTRACT
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
Subject(s)
Molecular Epidemiology , Gene Frequency , Genetic Counseling , Hospitals, University , Infant, Newborn , Karyotyping , Maternal Age , Mosaicism , Referral and Consultation , CytogeneticsABSTRACT
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.
Subject(s)
Down Syndrome/genetics , Nondisjunction, Genetic , Nucleolus Organizer Region/genetics , Nucleolus Organizer Region/ultrastructure , Abortion, Spontaneous/genetics , Adult , Case-Control Studies , Child, Preschool , Egypt , Female , Humans , Infant , Infant, Newborn , Karyotyping , Male , Maternal Age , Middle Aged , Parents , Pedigree , PregnancyABSTRACT
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
