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For further information, see CMDT Part 42-17: Down Syndrome
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Essentials of Diagnosis
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Typical craniofacial features (flat occiput, epicanthal folds, large tongue)
Intellectual disability
Congenital heart disease (eg, atrioventricular canal defects) in 50% of patients
Three copies of chromosome 21 (trisomy 21) or a chromosome rearrangement that results in three copies of a region of the long arm of chromosome 21
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General Considerations
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Maternal age is risk factor of increasing the chance of having a child with Down syndrome
Risk increases exponentially with the age of the mother at conception
Risk rises markedly after age 35
By age 45 years, the odds of having an affected child are as high as 1 in 40
The risk of other conditions associated with trisomy also increases because of the predisposition of older oocytes to nondisjunction during meiosis
Increased paternal age is not associated with risk of trisomy
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Nearly 0.5% of all human conceptions are trisomic for chromosome 21
Because of increased fetal mortality, birth incidence of Down syndrome is 1 per 700 but varies from 1 per 1000 in young mothers to more than three times as frequent in women of advanced maternal age
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Cytogenomic analysis
Prenatal detection
"Multiple marker screening" (screening maternal serum for alpha-fetoprotein and other biomarkers) in the first trimester or early in the second trimester
Ultrasonography can visualize increased nuchal thickness and underdevelopment of the nasal bone
Assaying fetal DNA that is circulating in maternal blood can diagnose Down syndrome with high sensitivity and specificity
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Duodenal atresia should be treated surgically
Congenital heart disease should be treated as in any other patient
Any leukemia typically responds to reduced-dose chemotherapy
No medical treatment has been proven to affect the neurodevelopmental or the neurodegenerative aspects
Supplementation with antioxidants has shown no benefit
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Patients who survive childhood and in whom dementia develops have a reduced life expectancy; on average, they live to about age 55 years
The intestinal and cardiac anomalies usually respond to surgery
A transient neonatal leukemia generally responds to conservative management
If relapse of leukemia occurs, outcome is poor
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For comprehensive evaluation of infants to investigate congenital heart disease, hematologic malignancy, and duodenal atresia
For genetic counseling of the parents
For ...