ATP1A3 and Areflexia: An increasing number of studies has demonstrated that some ATP1A3 mutations could lead to a range of clinical phenotypes, including alternating hemiplegia of childhood (AHC); rapid-onset dystonia-parkinsonism (RDP); cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS) syndrome; epilepsy; relapsing encephalopathy with cerebellar ataxia (RECA); fever-induced paroxysmal weakness and encephalopathy (FIPWE); early infantile epileptic encephalopathy (EIEE) and childhood-onset schizophrenia (COS).