Now identified as one of the most common causes of HSP, SPG7-associated disease has been linked to additional neuro-ophthalmologic features, including isolated dominant optic atrophy, cerebellar eye signs (various forms of nystagmus, dysmetric saccades), progressive external ophthalmoplegia (PEO), and supranuclear vertical palsy. The gene discussed is SPG7; the disease is hereditary spastic paraplegia.