FOXG1 and Rett syndrome: In this variant RTT group of patients, some have mutations in other genes that are also associated with RTT: cyclin-dependent kinase-like5 (CDKL5; MIM *300203), which is described in individuals with an early seizure onset variant of RTT13, and Forkhead box protein G1 (FOXG1; MIM *164874), which is responsible for the congenital variant of RTT14.