Beyond the focus of this study on common CNVRs for early-onset (extreme) obesity, we also explored selected regions harbouring rare CNVs (20,21). First, we looked at deletions on chromosome 16p11.2 (28.4–31.0 Mb) of at least 593 kb in both of our GWAS samples (21). In the family-based GWAS sample, we exclusively found one obese patient with a heterozygous de novo deletion of 709 kb. Moreover, in the case–control GWAS sample, four obese cases but none of the controls were called for heterozygous deletions with sizes between 709 and 894 kb (one-sided P-value of Fisher's exact test = 0.13). Secondly, we compared the list of rare recurrent CNVs found in patients with severe early-onset obesity (20) to the common CNVRs determined here. We observed no exact overlap, which was not unexpected given our focus on common CNVs. However, 2 of the 12 CNVs reported for patients with severe early-onset extreme obesity (20) were 133 kb downstream and 66 kb upstream of the CNVRs detected here (CNVR 3p11.1 and CNVR 15q13.2; Table 2). Both these CNVRs showed evidence for association with obesity
