Spastic ataxia with congenital miosis is a rare hereditary ataxia characterized by an apparently non-progressive or slowly progressive symmetrical ataxia of gait, pyramidal signs in the limbs, spasticity and hyperreflexia (especially in the lower limbs) together with dysarthria and impaired pupillary reaction to light, presenting as a fixed miosis (with pupils that seldom exceed 2 mm in diameter and dilate poorly with mydriatics). Nystagmus may also be present.