Monosomy 21 syndrome: Further delineation including clinical, neuropathological, cytogenetic and biochemical studies

Abstract
Only 6 cases of living newborns with apparently complete monosomy 21 have been reported. All the previous cases with the exception of the present case died between 3 wk and 20 mo. Only one of these cases had a postmortem examination. The subject of this report was previously described at the age of 6 yr. He survived until 11 yr old and is the oldest known case of complete monosomy 21. The clinical presentation over 11 yr, results of gene dosage studies, cytogenetic analysis and the neuropathological postmortem examination are presented.