| A rare X-linked syndromic intellectual disability disease with characteristics of neonatal hypertonia which evolves to hypotonia and an exaggerated startle response (to sudden visual, auditory or tactile stimuli), followed by the development of early-onset, frequently refractory, tonic or myoclonic seizures. Progressive epileptic encephalopathy, intellectual disability, and psychomotor development arrest, with subsequent decline, may be additionally associated. There is the disease is caused by mutation in the ARHGEF9 gene on chromosome Xq22.1. |
