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Introduction Down syndrome (DS) is the most common chromosomal disorder. It is accompanied by several comorbidities, which could lead to severe morbidity and mortality. Congenital heart disease (CHD) is one of the most commonly described condition. Objective This study aimed to determine clinical profiles, dysmorphic features, CHD, and DS associated comorbidities in a tertiary center (Cairo, Egypt). Patients and Methods This descriptive study included 290 patients diagnosed with DS, who presented to the Clinical Genetics clinic, Cairo University Children Hospitals, from February 2018 to December 2019. The patients' ages ranged from 2 to 4 years old. All patients were evaluated by full history, clinical examination, anthropometric measurements, and assessment of developmental milestones. Patients' diagnostic investigations including karyotype, thyroid function, and echocardiography were checked. Results The study population consisted of 290 children with DS of which 196 (67.6%) were male, 115 (40%) had CHD, the most prevalent atrial septal defect (ASD), patent ductus arteriosus (PDA), and ventricular septal defect (VSD) accounting for 10.7, 7.1, and 4.2%, respectively. Common dysmorphic features were upward slanting palpebral fissures (98.6%), hypertelorism (97.9%), and sandal gap (60.7%). Thyroid dysfunction was the second prevalent comorbidity, found in 35 patients (12.1%). Global developmental delay was reported affecting language (99%), motor (94.8%), and social (92.8%) domains. Conclusion The prevalence of CHD among children with DS was 40% with ASD, PDA, and VSD being the commonest. Thyroid dysfunction was the second most common comorbidity. The most prevalent dysmorphic features were upward slanting palpebral fissures, hypertelorism, and sandal gap. Developmental delay was very common, language being the most affected domain.

Background: Maternal age influences the type of chromosomal anomaly in Down syndrome. The older age is associated with non-disjunction while the younger age is associated with translocation of chromosome 21. Aim of the Work:To study the cytogenetics of children with Down syndrome born to the young mother who presented to Pediatrics Genetics Unit at Cairo University Children Hospital during one year (2019), and compare with those born to an older mother. Materials and Methods: This descriptive retrospective study analyzed records of 210 children with Down syndrome who presented to Pediatrics Genetics Unit at Cairo University Children Hospital during 2019. Results: Among the total 210 studied children with Down syndrome, 21(10%) were born to young mothers aged 21 years or less at conception. Seven (33.34%) were males and 14 (66.6%) were females. Twenty (95.2%) were first born to a young mother, only 1 was a second born. Karyotyping proved that 6 (28.6%) had Robertsonian translocation of trisomy 21, and 15 (75.4%) had non-disjunction. Only 1 (4.76%) of children born to younger mothers had associated cardiac anomalies, while among those born to the older mother 40 (21%) had associated anomalies, of them were cardiac 36 (19.04%), hydrocephalus in one (0.5%), and ambiguous genitalia in 3 (1.58%) (p=0.072). First born trisomy 21 were 109 (51.9%) among the whole studied cohort, with a mean maternal age +/-SD of 30.2 years +/-7.35 years, their karyotyping was non-disjunction, Robertsonian translocation and mosaic in 100, 5 and 3 respectively. Cardiac anomalies were encountered among 18 (16.5%). Conclusion:Children born with trisomy 21 to mothers younger than 21 at conception are mostly due to non-disjunction. First born children with trisomy 21 comprised half the studied cohort of trisomy 21. Further studies to define preventable causes of non-disjunction in the young mother, are needed to reduce the incidence of Down syndrome.