title: Identical monochorionic twins with down syndrome and paternal origin of the extra chromosome 21.
abstract: Trisomy 21, the cause of Down syndrome (DS), is the most frequent trisomy in humans. The risk for DS increases with maternal age: mothers under 25 years of age are known to have an average risk of a DS pregnancy of 1: 1600, rising to 1: 350 at age 35 and to 1: 40 at 43, respectively. Twins with DS are rare. We report on monozygotic (MZ), monochorionic twin sisters with DS, whose parents are young (24 and 26 years old, respectively) and healthy. Family history is non contributory; pregnancy and delivery were uneventful. Both girls presented at birth with clinical manifestations of Down syndrome, that was confirmed cytogenetically (47XX,+21). Microsatellites analysis indicated that the twins are identical and that the extra chromosome 21 was of paternal origin.
  
  
  CONCLUSIONS
  For practical purposes, the causative non disjunction should be considered a single sporadic event, with an empirical recurrence risk estimated at about 1%.
authors: Medical Faculty Skopje, 50 Divizija BB, Skopje, R. Macedonia.
authors: A
authors: A
authors: Urumova
authors: Velibor
authors: V
authors: Tasic
authors: E
authors: E
authors: Bojadjieva
authors: M G
authors: MG
authors: Pomponi
authors: G
authors: G
authors: Neri
authors: Z
authors: Z
authors: Gucev
mesh_terms: D002891:Chromosomes, Human, Pair 21; D004200:Diseases in Twins / Q000235:genetics*; D004314:Down Syndrome / Q000235:genetics*; D005220:Fathers; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D012307:Risk Factors; D014430:Twins, Monozygotic