Characterization of a supernumerary marker derived from chromosome 17 by microdissection in an adult with MR/MCA.

We describe a 38-year-old adult who has a supernumerary marker chromosome in 40% of metaphase cells which was identified by reverse in situ hybridization with a DNA probe made by microdissection to be derived from chromosome 17. The breakpoints are estimated by G-banding and fluorescence in situ hybridization (FISH) to consist of the region from 17p11.1 to proximal 17q21. The propositus displayed severe growth retardation, kyphoscoliosis, bilateral cataracts, severe calcaneovalgus deformity of the feet, dysmorphic facies, profound mental retardation, and multiple medical problems requiring ongoing medical management. These problems included a mitral valve prolapse with regurgitation, recurrent upper and lower respiratory tract infections, and severe respiratory insufficiency. The relatively long survival of this patient enabled us to describe the natural history of this rare chromosomal mutation.