Mosaicism and the trisomy 8 syndrome

Three new cases of trisomy 8 mosaicism are presented; two have features corresponding with those usually found in this syndrome, whereas one is highly atypical. In view of the almost universal mosaicism of these patients, the literature is reviewed with an emphasis on the patterns of mosaicism found. There is little correlation between degree of mosaicism and extent of clinical abnormality. The degree of mosaicism differs in different tissues, fibroblasts being more informative of aneuploidy than lymphocytes, and there is some evidence that the degree of mosaicism varies with time. The reasons for these findings are discussed, with particular reference to the raised paternal age found in a proportion of the reported cases.