Trisomy 2q11.2→q21.1 resulting from an unbalanced insertion in two generations

In this communication, we describe two cases of proximal 2q trisomy (2q11.2-->q21.1) resulting from an interchromosomal insertion. The chromosomal origin of the insertion was confirmed by fluorescence in situ hybridisation. An unbalanced karyotype, 46,XX, der(8), ins(8;2)(p21.3; q21.1q11.2),was found in the proband and her mother, who both have mild mental retardation, short stature, dysmorphic features, insulin dependent diabetes mellitus, and a psychotic illness. This family is a rare example of direct transmission of a partial autosomal trisomy.