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    Am J Med Genet Suppl. 1990;7:186-8.

    Trisomy 21 mosaicism in gonads with unexpectedly high recurrence risks.

    Source

    Department of Clinical Genetics, University Hospital Dijkzigt, Erasmus University, Rotterdam, The Netherlands.

    Abstract

    The recurrence risk for Down syndrome (DS) is about 1% in case of a previous offspring with trisomy 21 and minimal in case of a de novo (21;21) translocation. We have monitored 1,211 pregnancies in the first and second trimester after a prior occurrence of trisomy 21. Six couples had a trisomy 21 fetus in a subsequent pregnancy. We studied their lymphocytes, fibroblasts, and in one case ovaries, to detect parental mosaicism for chromosome 21. We detected mosaicism in 2 parents with 3 and 4 pregnancies, respectively, in which trisomy 21 was found. In one it was present in 47% of cells from the ovaries. Another couple with a pregnancy monitored because of a first child with a de novo (21;21) translocation had normal chromosomes themselves and one normal child, but 2 more pregnancies with a (21;21) translocation. It is concluded that thorough cytogenetic study of parents is indicated after 2 pregnancies with regular or translocation trisomy of chromosome 21. Genetic counseling should consider the possibility of an elevated recurrence risk due to gonadal mosaicism in one parent.

    PMID:
    2149943
    [PubMed - indexed for MEDLINE]

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