Karyotypes and Case Studies of 17 Down's Syndrome Individuals
DesJardin, Patrick John
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The problem. Sixteen patients suspected of having mosaic Downs syndrome and one suspected of having a translocation Down's syndrome were studied by chromosome analysis at Woodward State Hospital, Woodward, Iowa during June and July of 1973. Procedure. A cytogenetic analysis was made of chromosomes prepared from leucocyte cultures from peripheral blood. At least 30-50 cells were counted and karyotypes made for each patient. Findings. The cell counts and karyotypic studies verified the presumption that 16 patients had mosaic Down's syndrome and that one patient had translocation Down's syndrome. The chromosome counts showing 46 chromosomes in the mosaic individuals were normal chromosome complements. The individual shown to have a translocation type of Down's syndrome appeared to be carrying an unbalanced translocation involving ohromosome 14 and an extra ohromosome number 21. Conclusion. The observed frequency of 1.15% of translocation Down's syndrome at Woodward is lower than the 3-4% reported by other investigators. The 18.4% frequency for mosaic type Down's at Woodward is much higher than the 1-2% reported by other authors. The mean age found for those individuals with mosaicism in this study is higher than those with trisomy 21, although it is not statistically significant. No significant difference in the prevalence of mosaics among patients born to young or old mothers was evident. Recommendations. A follow-up study to determine if the mortality rate of mosaic type Down's syndrome individuals is significantly lower than those with trisomy 21 is recommended.