AP5Z1 and hereditary optic atrophy: The diagnosis of Alexander's disease is established with a heterozygous pathogenic variant inGFAPidentified by molecular genetic testing.49There are rare cases described of non-epileptic myoclonus, affecting patients with SPG4, SPG7, SPG35, SPG48, and SPOAN (spastic paraplegia, optic atrophy, and neuropathy).5, 33, 50, 51, 52