In a developmentally delayed girl with an autism spectrum disorder, Single nucleotide polymorphism (SNP) array analysis showed a de novo 280 kb deletion on chromosome 16q23.2 involving two genes, GAN and CMIP. Inactivating mutations in GAN cause the autosomal recessive disorder giant axonal neuropathy, not present in our patient. CMIP was recently implicated in the etiology of specific language impairment by genome-wide association analysis. It modulates phonological short-term memory and hence plays an important role in language acquisition. Overlaps of specific language impairment and autism have been debated in the literature regarding the phenotypical language profile as well as etiology. Our patient illustrates that haploinsufficiency of CMIP may contribute to autism spectrum disorders. Our finding further supports the existence of a genetic overlap in the etiology of specific language impairment and autism. Autism Res 2012, 5: 277–281. © 2012 International Society for Autism Research, Wiley Periodicals, Inc.