ATP1A3 and Leber hereditary optic neuropathy: Extensive neurological investigations carried out on these patients resulted in normal.[68] Demos et al.[57] in 2014 identified in a proband affected by cerebellar ataxia, areflexia, pes cavus, optic atrophy, sensorineural hearing loss (CAPOS) syndrome, and in his affected sister and mother a novel heterozygous missense mutation, c.2452G> A (p.Glu818Lys), in the ATP1A3 gene.