A case of mosaic trisomy 19q12-q13.2 with high BMI, macrocephaly, and speech delay: does USF2 determine size in the 19q phenotypes?

Hall et al. (2010) describe a boy with mosaic trisomy of the proximal part of 19q, with obesity, macrocephaly and global developmental delay. The patient is interesting with regard to his cytogenetic abnormality, which is smaller than those previously reported, and does not include the candidate obesity and insulin-resistance genes identified by other authors (Zung et al., 2007; Davidsson et al., 2010) as possible causes of the overweight/obesity seen in four of five previously documented patients. This suggests that a novel obesity locus may reside in the duplicated region 19q13.11–q13.2. We present a phenotypically similar boy with intrachromosomal insertion of material derived from proximal 19q into proximal 19p, causing mosaic trisomy 19q12–q13.2, and consider the role of USF2, a master transcriptional regulator of metabolic genes, in 19q phenotypes.