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Difference between revisions of "Down syndrome"
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'''Down syndrome''', is a common genetic abnormality. It may also be called '''Trisomy 21'''; however, technically this may not be completely correct in all cases. | '''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:<ref name=Ref_PCPBoD8_99>{{Ref PCPBoD8|99}}</ref> | |||
{| class="wikitable sortable" | |||
! 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== | ==Characteristics== | ||
| Line 21: | Line 41: | ||
Notes: | Notes: | ||
*Brushfield spots = white/grey spots in the iris (the "colour part" of the eye). | *Brushfield spots = white/grey spots in the iris (the "colour part" of the eye). | ||
<gallery> | |||
Image:Brushfield_eyes_magnified.jpg | Brushfield spots. (WC) | |||
</gallery> | |||
===Simplified=== | |||
Simplified version of mnemonic ''CHILD HAS PROBLEM'': | |||
#[[congenital heart disease|'''C'''ongenital heart disease]]. | |||
#'''H'''ypothyroidism. | |||
#'''I'''ncurved 5th digit (clinodactyly) / Increased gap between 1st and 2nd toe. | |||
#[[Leukemia|'''L'''eukemia]] risk x2. | |||
#'''D'''uodenal atresia. | |||
#[[Hirschsprung disease|'''H'''irschsprung disease]]. | |||
#[[Alzheimer disease|'''A'''lzheimer disease]] / Alantoaxial instability. | |||
#'''S'''hort neck. | |||
#'''P'''almar crease / Protruding [[tongue]]. | |||
#'''R'''ound face. | |||
#'''O'''cciput flat / Oblique eye fissure. | |||
#'''B'''rushfield spots / Brachycephaly. | |||
#'''L'''ow nasal bridge. | |||
#'''E'''picanthic fold / Ears folded. | |||
#'''M'''ental retardation. | |||
==See also== | ==See also== | ||