A recurrent 16p12.1 microdeletion supports a two-hit model for severe developmental delay

Evan Eichler and colleagues identify a recurrent microdeletion on 16p12.1 associated with developmental, cognitive and neuropsychiatric phenotypes. They also show that more severe phenotypes are frequently correlated with the presence of a second large genomic rearrangement, supporting a complex model of pathogenesis that may underlie the variable expressivity typical of many microdeletion syndromes.