Direct duplication of 8p21.3-->p23.1: a cytogenetic anomaly associated with developmental delay without consistent clinical features.

We report six cases in two families and a sporadic case with a direct duplication of region 8p21.3-->23.1. In one family, the duplication started in the mother and was transmitted to one son and one daughter. In the second family, the father was mosaic for the anomaly that was transmitted to his two daughters. The cytogenetic anomaly was initially described as an 8p+ with banding analysis and then delineated with fluorescence in situ hybridization (FISH) using whole-chromosome 8 painting, 8p specific painting, and 8p or 8p/8q subtelomeric probes. Deletion was not detected in the subtelomeric region of the abnormal chromosome 8 examined in one family and in the sporadic case. The phenotypic picture varies from normal to moderate mental retardation in the affected individuals. No consistent minor anomalies or congenital defects were observed among these cases. After comparing the chromosome region involved in our cases with those in others having direct or inverted duplications of 8p, it is thought that the segment 8p21.1-->21.3 might be the critical region for an 8p duplication syndrome. The parental origin of the duplication does not seem to impact its clinical significance. Copyright 2001 Wiley-Liss, Inc.