Translocation Down's syndrome.

Among the 500 Down syndrome children karyotyped, 15 (3%) were due to translocation; 10 were 21;21 translocation and five 14;21. There were 9 cases of de novo translocations, while 6 were inherited from father or mother. Family history was characteristic in all the translocation cases, with younger parental age, fetal wastage in the family, recurrence and with the affected child often being either the first or the only liveborn in the family. The pattern of translocation in Madras and the significance of family history in genetic counselling are discussed.