RT Book, Section
A1 Harris, David J.
A1 Alkuraya, Fowzan S.
A2 Murray, Michael F.
A2 Babyatsky, Mark W.
A2 Giovanni, Monica A.
A2 Alkuraya, Fowzan S.
A2 Stewart, Douglas R.
SR Print(0)
ID 1102706929
T1 Down Syndrome
T2 Clinical Genomics: Practical Applications in Adult Patient Care
YR 2014
FD 2014
PB McGraw-Hill Education
PP New York, NY
SN 9780071622448
LK accessbiomedicalscience.mhmedical.com/content.aspx?aid=1102706929
RD 2024/04/23
AB Disease  summary:Down  syndrome  (DS)  is  a  chromosomal  aneuploidy  of  chromosome  21  and  represents  the  most  frequently  identified  cause  of  intellectual  disability,  with  a  wide  range  of  severity.In  addition  to  typical  facial  features,  the  phenotype  includes  skeletal,  neurologic,  gastrointestinal,  endocrine,  and  hematologic  components  or  risks.  Anticipatory  guidance  is  the  key  to  the  prevention  and  treatment  of  these  complications.DS  is  associated  with  increased  mortality  in  childhood  (usually  due  to  congenital  heart  disease)  and  in  adulthood  (due  to  Alzheimer  disease  and  premature  aging,  among  other  factors).Prenatal  screening  for  DS  is  widely  practiced  and  has  evolved  from  ultrasound-based  approach  to  combined  ultrasound  and  biochemical  marker-based  approach  to  DNA-based  approach.Hereditary  basis:DS  is  usually  caused  by  the  sporadic  de  novo  occurrence  of  a  meiotic  error  involving  chromosome  21  in  the  parent  (usually  the  mother  especially  in  the  older  age  group),  which  is  associated  with  a  low  recurrence  risk.A  much  higher  recurrence  risk  is  observed  when  the  meiotic  error  is  the  result  of  a  constitutional  parental  translocation  (<5%  of  DS  cases)  or  parental  mosaicism  (frequency  unknown).Differential  diagnosis:Single  palmar  (Simian)  crease,  sandal  gap,  upslanting  palpebral  fissures,  epicanthic  folds,  protruding  tongue,  and  hypotonia  are  seen  in  the  majority  of  DS  but  can  also  be  seen  in  normal  individuals  and  this  explains  why  clinical  diagnosis  is  only  accurate  in  two-thirds  of  the  cases  in  the  neonatal  period.  Hypothyroidism  may  present  with  similar  features.  Other  rare  disorders,  such  as  peroxisomal  disorders  and  Menkes  syndrome  are  possible  alternatives  in  infants.  Short  stature  and  mental  retardation  occur  in  a  number  of  disorders.