Microcephaly-Corpus Callosum and Cerebellar Vermis Hypoplasia-Facial Dysmorphism-Intellectual Disability Syndrom An important gene associated with Microcephaly-Corpus Callosum and Cerebellar Vermis Hypoplasia-Facial Dysmorphism-Intellectual Disability Syndrom is RAC1 (Rac Family Small GTPase 1). Affiliated tissues include brain and heart, and related phenotypes are intellectual disability and global developmental delay