Down syndrome child with 48,XXY,+21 karyotype.

Cytogenetic analysis in 60 clinically suspected cases of Down syndrome and their parents was carried out using conventional Giemsa-trypsin-banding technique. Fifty-five individuals (91%) exhibited a free trisomy 21. Robertsonian translocations were seen in three cases and two cases exhibited a normal karyotype. A four-month-old child, the second-born of non-consanguineous parents, possessed an extra X chromosome in addition to trisomy 21. The proband's parents and his brother showed a normal karyotype. The phenotypic characteristics of this child have been discussed in the light of the published reports on double aneuploidies of XXY and trisomy 21.