CAPOS syndrome is a very rare autosomal dominant disorder whose name derives from an acronym of its cardinal symptoms: cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss.

CAPOS syndrome is a progressive disease that begins in childhood with episodes of febrile encephalopathy and ataxia, which do not fully resolve. The associated visual and hearing impairments also progress throughout childhood.

Acute episodes do not typically continue into adulthood, but neurologic decline remains progressive. Some patients have no associated cognitive deficits, while others have behavioral disorders resembling autism. No abnormalities have been identified through brain imaging.