Down syndrome (trisomy 21)
Incidence 1:800 (US), the most common chromosomal abnormality |
Causes
95% trisomy, 4% Robertsonian transloc, 1% mosaicism |
Neonatal
Severe hypotonia, abnormal facial features
Limbs
Short/curved 5th finger, single palmar crease
Cardiovascular
ASD (Ost. prim.), VSD, PDA, AV canal defects
GIT
Duodenal and anal atresia, Hirschsprung D
Other
⇓stature, ⇓cognitive ability, strabismus, Alzheimer's (late) |
Turner syndrome (45,X)
Liveborn incidence 1-2:10,000 |
Caused by absent Barr body |
Neonatal
1. Low post. hairline
2. ⇑Elbow carry angle
3. Short 4th metacarpals
4. Widely spaced nipples
5. Aortic coarctation |
Later complications
1. ⇓Stature
2. Infertility (SHOX gene rel.) |
USG 2nd trim: Hydrops fetalis, thickened nuchal pad |
Patau & Edwards syndromes (trisomies 13, 18)
Incidence 1:5000 (each), ⇑w/ maternal age |
10% from mosaicism+Robertsonian transloc |
Most term. when discovered, or stillbirth |
Most liveborn die within days-weeks |
Late complications
1. Cardiac defects (90%)
2. Learning difficulties |
Klinefelter syndrome (47,XXY)
1:1000 live births |
Common features
1. Tall
2. ⇓Verbal IQ 10-20pts
3. Gynecomastia
4. Azoospermia⇒infert. (ALL patients)
5. Small, soft testes |
Rarely: >2 X chromosomes (XXXY, XXXXY)⇒⇓⇓cognitive ability, other features more pronounced |
Triploidy (69,XXX, 69,XXY, 69,XYY)
Common in stillbirth |
Rare in live births, rarely live beyond neonatal period |
Hypomelanosis of Ito
Mosaicism w/ triploid cell line
Presentation
1. Pigmented+unpigmented streaks on skin
2. Learning difficulties
3. Hard-to-treat convusions |
|
|
|
