Hyperekplexia and epilepsy is also known as early infantile epileptic encephalopathy 8 (EIEE8) [DS:H00606]. It is an X-linked mental retardation and sensory hyperarousal, caused by mutations in ARHGEF9. Collybistin, encoded by ARHGEF9, is a RhoGEF family protein and highly expressed in the developing and adult brain.
