A rare chromosome 5 heterochromatic variant derived from insertion of 9qh satellite 3 sequences.

A rare chromosome 5 heterochromatic variant not linked to any clinical sign was identified in a three-generation family. After performing conventional cytogenetics characterization, fluorescence in situ hybridization of D9Z1 indicated that the unusually large qh region of chromosome 5 originated from 9qh, whereas the centromere of the variant chromosome was 5-specific as demonstrated by primed in situ DNA labelling. FISH of probes targeting satellite 3 and beta-satellite sequences of 9qh showed that only satellite 3 sequences were present in the variant 5qh region.