title: The occurrence of a ring 18, an accessory bisatellited fragment, and trisomy 21 within one sibship.
abstract: A family is presented in which there were three different chromosome abnormalities in the children although the parents were cytogenetically normal. The proband had the karyotype 46,XX, r(18) (p11q23), a phenotypically normal brother was 47,XY,+mar, and another brother was a typical case of Down's syndrome, karyotype 47,XY,+21. There is nothing in the parents' history that provides grounds for a hypothesis to explain the coincidence of the abnormalities.
mesh_terms: D002478:Cells, Cultured; D002869:Chromosome Aberrations / Q000235:genetics*; D025063:Chromosome Disorders; D002902:Chromosomes, Human, 16-18; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D007621:Karyotyping; D008214:Lymphocytes / Q000648:ultrastructure; D008297:Male; D010375:Pedigree; D012867:Skin / Q000648:ultrastructure