Characterization of mosaic supernumerary ring chromosomes by array-CGH: segmental aneusomy for proximal 4q in a child with tall stature and obesity.

We report on a 6-year-old girl with developmental delay, tall stature, and obesity. G-banded chromosome analysis revealed mosaicism for one to three small de novo rings in 82% of peripheral lymphocytes. Fluorescence in situ hybridization (FISH) studies and metaphase comparative genomic hybridization (CGH) demonstrated that the rings were derived from 4q10-4q13. A higher resolution investigation was initiated using array-CGH analysis and revealed a gain of 11 adjacent clones spanning a 16 Mb region at 4q11-q13.2 and including the insulin-like growth factor binding protein 7 (IGFBP7) gene. This finding suggests that postnatal overgrowth observed in our patient might be related to a dosage effect of the IGFBP7 gene.