Down syndrome
Jump to navigation
Jump to search
The printable version is no longer supported and may have rendering errors. Please update your browser bookmarks and please use the default browser print function instead.
Down syndrome, abbreviated DS, is a common genetic abnormality. It may also be called Trisomy 21; however, technically this may not be completely correct in all cases.
Genetics
Down syndrome can be the result of three different defects:[1]
| Defect | Percent of DS | Notes |
|---|---|---|
| Extra chromosome 21 (trisomy 21) | ~95% | defect seen more often with increasing maternal age |
| Robertsonian translocation | ~4% | part of chromosome 21 attaches to chromosome 22 or 14; one parent is a carrier -- recurrence virtually 100%; no age dependence |
| Mosaicism | ~1% | some cells have a triple dose of chromosome 21 while others have a normal number of chromosome 21; no age dependence |
Characteristics
Mnemonic CHILD HAS PROBLEM:[2]
- Congenital heart disease / Cataracts.
- Hypothyroidism / Hypotonia.
- Incurved 5th digit (clinodactyly)[3] / Increased gap between 1st and 2nd toe.
- Leukemia risk x2 / Lung problem.
- Duodenal atresia / Delayed development.
- Hirschsprung disease / Hearing loss.
- Alzheimer disease / Alantoaxial instability.
- Short neck / Squint.
- Palmar crease / Protruding tongue.
- Round face / Rolling eye (nystagmus).
- Occiput flat / Oblique eye fissure.
- Brushfield spots / Brachycephaly.
- Low nasal bridge / Language problems.
- Epicanthic fold / Ears folded.
- Mental retardation / Myoclonus.
Notes:
- Brushfield spots = white/grey spots in the iris (the "colour part" of the eye).
Brushfield spots. (WC)
Simplified
Simplified version of mnemonic CHILD HAS PROBLEM:
- Congenital heart disease.
- Hypothyroidism.
- Incurved 5th digit (clinodactyly) / Increased gap between 1st and 2nd toe.
- Leukemia risk x2.
- Duodenal atresia.
- Hirschsprung disease.
- Alzheimer disease / Alantoaxial instability.
- Short neck.
- Palmar crease / Protruding tongue.
- Round face.
- Occiput flat / Oblique eye fissure.
- Brushfield spots / Brachycephaly.
- Low nasal bridge.
- Epicanthic fold / Ears folded.
- Mental retardation.
See also
- Trisomy 13 (Patau syndrome).
- Trisomy 18 (Edwards syndrome).
- Chromosomal anomalies.
- Stillbirth.
References
- ↑ Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 99. ISBN 978-1416054542.
- ↑ URL: http://www.valuemd.com/genetics.php. Accessed on: 29 May 2011.
- ↑ URL: http://www.handresearch.com/diagnostics/simian-line-down-syndrome.htm. Accessed on: 29 May 2011.