A patient with a de novo t(6;9) and an interstitial duplication of (9)(q21.2q22.1)

We report on a 4-year-old child with psychomotor retardation, general hypot onia and only mild dysmorphic features. Her chromosome constitution was 46, XX, t (6;9) (q27;q22.1), dup (9)(q21.2q22.1). This de novo interstitial dup lication was confirmed using fluorescence in situ hybridisation (FISH) with band-specific probes. This is the second report of a patient with an inter stitial duplication of this region of the long arm of chromosome 9. It is c oncluded that in a child with an abnormal phenotype and a de novo (apparent ly) balanced translocation, the possibility of a small duplication or delet ion should be considered. Clin Dysmorphol 8: 211-214 (C) 1999 Lippincott Wi lliams & Wilkins.