Variants of chromosome 9 with additional euchromatic bands: two case reports.

This paper documents a prenatal case of maternally inherited subtle duplication of chromosome 9 bands q21.1 to q21.2 and a second case with two G-bands within the 9qh region. Cytogenetic studies of these cases included G-banding, C-banding, fluorescent in situ hybridization (FISH) using chromosome 9 specific library probe, and the classical satellite probe. In both patients, the additional bands were G-bands and C-band negative. By FISH studies they were negative for the satellite heterochromatin probe and positive for the chromosome 9 painting probe. Therefore, the extra bands were presumably euchromatin and part of chromosome 9. The chromosome 9 variants and their possible mechanisms of origin are discussed.