Cerebellar ataxia is common in myoclonic epilepsy with ragged red fibers (MERFF) due to mutations in the mitochondrial transfer RNA (tRNA) lysine gene, in Kearns-Sayre syndrome due to mtDNA deletions, in sensory ataxic neuropathy with dysarthria and ophthalmoplegia (SANDO) due to nuclear POLG1 gene mutations, and also in ARCA2, Friedreich's ataxia, SPG7, SCA28 and autosomal-recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) due to mutations in nuclear genes involved in mitochondrial morphology or function.
Our findings widen the spectrum of SPG7 mutations of ARHSP and indicate that the SPG7 mutation is an important cause of adult-onset undiagnosed ataxia.
Additional clinical features were noted, including optic atrophy and ataxia for patients with SPG5 and ataxia and a chronic progressive external ophthalmoplegia-like phenotype for SPG7.