Partial trisomy 17q. Karyotype: 46,XY,der(21),t(17;21)(q22;p13)

A 15-year-old deeply mentally retarded male is described with partial distal 17q trisomy (17q22 replaced by 17qter),as the result of a de novo 17q/21p translocation. Differential Ag-staining showed that the satellites of chromosome 21 were included in the translocation chromosome.