Centre for Human Genetics, U.Z. Gasthuisberg, Leuven, Belgium.
In this report we present a 3-year-old girl with partial trisomy of the long arm of chromosome 16 due to a direct duplication 16q11.1----q13 (karyotype: 46, XX, dir dup(16) (pter----cen----q11.1----q13::q11.1----q13::q13----qter]. She presented moderate mental retardation and severe hyperkinetic behaviour. Slight dysmorphic stigmata but no internal anomalies were found.