Inverted tandem duplication generates a duplication deficiency of chromosome 8p

An adult female with severe mental retardation and dysmorphic features is described. A de novo chromosomal aberration involving 8p was found. The karyotype was 46, XX, inv dup (8) (pl2p23.1). Dosage studies with the DNA probe D8S7, which is located at 8p238pter, showed that the patient was monosomic for this marker. Thus the de novo rearrangement generated a duplication-deficiency chromosome. The possible mechanisms of formation of this abnormal chromosome are discussed.