Mongolism and Other Abnormalities in a Family with Trisomy 21–22 Tendency

Summary An example of trisomy 21–22, idiocy and some malformations is described and compared with the other non‐mongoloid trisomies 21–22. The difficulty is discussed of making a correct morphological identification of the chromosome in the smallest chromosome group. The present patient resembles two previously reported non‐twin sisters, both having an extra chromosome similar to, although not quite identical with, the chromosomes in group 21–22. In the present patient's family, there has also been more than one instance of trisomy. A hypothetical explanation of a non‐disjunction tendency in families with supposed translocations and in families with normal karoytypes is given.