Trisomy 21

Question 1

What genetic patterns are possible for Trisomy 21?

Answer 1

3% unbalanced translocation between chromosome 21 and another chromosome
75% sporadic
25% familial
Mosaicism

Question 2

What are the clinical manifestations for Trisomy 21?

Answer 2

1. Characteristic facies incld. epicanthal folds, upslanting palpebral fissures, flat nasal bridge, small ears
2. Cardiac malformation esp. AV canal defects
3. MR
4. Short stature
5. Bowel abnormalities e.g. duodenal atresia, Hirschprung’s disease
6. Flattened posterior skull e.g. brachycephaly
7. Brushfield spots (iris hamartomas)
8. Single palmar crease, 5th finger clinodactyly
9. Hypothyroidism
10. Leukemia
11. Early onset Alzheimer disease