Maternal transmission of translocation 2;21 associated with Down's syndrome.

An unusual 2;21 translocation associated with Down's syndrome is reported. The proband was a 3 year old boy, clinically diagnosed as having Down's syndrome and with a family history of Down's syndrome. Maternal age at the time of study was 28 years. Out of the four sibs with Down's syndrome three had died. Two pregnancies ended in first trimester miscarriage. The proband was found to have trisomy 21 associated with a 2;21 translocation inherited from his mother.