Identification and molecular confirmation of a small chromosome 10q duplication [dir dup(10)(q24.2-->q24.3)] inherited from a mother mosaic for the abnormality.

We describe a family in which two siblings exhibited developmental delay, reduced muscle tone and mild muscle weakness. Cytogenetic evaluation demonstrated that both children had a tandem duplication of a small portion of the long arm of-chromosome 10 [46,XX or XY,dir dup(10) (q24.2-->q24.3)], inherited from their clinically normal mother, who was found to be mosaic for the duplicated chromosome 10, Fluorescence in situ hybridization approaches, including total chromosome painting and the use of regional specific cosmid probes, were used to confirm the chromosome 10q origin of the duplicated material. This is the smallest confirmed duplication of this portion of chromosome 10 reported to date. (C) 1996 Wiley-Liss, Inc.