Microdeletions in 16p11.2 and 13q31.3 associated with developmental delay and generalized overgrowth

Chromosome microarray analysis of patients with developmental delay has provided evidence of small deletions or duplications associated with this clinical phenotype. In this context, a 7.1- to 8.7-Mb interstitial deletion of chromosome 16 is well documented, but within this interval a rare 200-kb deletion has recently been defined that appears to be associated with obesity, or developmental delay together with overgrowth. We report a patient carrying this rare deletion, who falls into the latter clinical category, but who also carries a second very rare deletion in 13q31.3. It remains unclear if this maternally inherited deletion acts as a second copy number variation leading to pathogenic variation, or is non-causal and the true modifiers are yet to be determined.