Other early-onset spastic ataxia conditions, like SPAX7 and SPAX4, HSP due to inherited neurometabolic disorders, and the group of sacsinopathies, including Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS), also constitute important differential diagnoses, although neuro-ophthalmic involvement with optic atrophy is less characteristic [7,8,43]. The gene discussed is MTPAP; the disease is hereditary optic atrophy.