Bisatellited extra small metacentric chromosome in newborns

Among 5,049 consecutive liveborn children in a Danish maternity hospital, three had an extra small bisatellited metacentric chromosome, apparently an isochromosome of the short arms of a D or G group chromosome. In two of the probands' families, the deviating chromosome was inherited through three generations. One proband was a mosaic; her grandmother, mother and one sister had the karyotype 46, XX,9qh+; one of her brothers had the karyotype 46, XY,9qh+, and he had one daughter with the karyotype 46, XX,9qh+ and another daughter who was 45, X. All the carriers of an extra metacentric chromosome were normally developed, except one proband who died shortly after birth and displayed multiple, internal congenital abnormalities.