Increased chromosome 21 mosaicism in older Down syndrome individuals
- New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY (United States); and others
Loss of one chromosome 21 in older Down syndrome individuals has been reported recently. During a study of the familial aggregation of Down syndrome and Alzheimer disease, our preliminary observations indicated increased mosaicism for the loss of a chromosome 21 in whole blood cultures from Down syndrome individuals who were age 50 or over from a cohort of 22 individuals. We retrospectively reviewed our experience in 189 cases of Down syndrome ranging in age from 1 day to 71 years. In a combined total of 212 individuals, 39 were age 50 or more of whom 7 or 18% were mosaic, while 169 were under age 50 of whom 4 or 2% were mosaic. Therefore the occurrence of mosaicism was strikingly increased in the group of individuals who were age 50 or over ({chi}{sup 2}=12.8, p<.001). Our observations confirm the above reports of increased mosaicism for chromosome 21 loss in lymphocyte cultures from older Down syndrome individuals. Since the older individuals were not karyotyped at birth, it is not possible to determine whether the age-related increase in mosaicism is due to increased survival of mosaic individuals or acquired mosaicism. Assuming 1% mosaicism at birth for Down syndrome and assuming the general population`s death rates for these mosaic individuals, life table methods showed that the expected proportion of these individuals at age 70 was 5%. This was less than 1/3 of our observations suggesting that acquired mosaicism was the predominant mechanism for our findings.
- OSTI ID:
- 133700
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0431
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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