Mutations in COA7 have been associated with spinocerebellar ataxia with axonal neuropathy type 3 and mitochondrial myopathy resulting from cytochrome c oxidase (complex IV) deficiency. Complex IV deficiency is a disorder of the mitochondrial respiratory chain with heterogeneous clinical manifestations, ranging from isolated myopathy to severe multisystem disease affecting several tissues and organs. In cases of pathogenic COA7 mutations, patient clinical manifestations can include sensory disturbance, decreased deep tendon reflexes, dysarthria, peripheral neuropathy, axonal sensorimotor neuropathy, ataxia, cerebellar and spinal cord atrophy, leukoencephalopathy, elevated serum creatine kinase levels, ragged-red fibers, and cognitive impairment. COA7 loss-of-function has been shown to lead to the disruption of oxidative phosphorylation, with cytochrome c oxidase activity being the most affected complex. Pathogenic variations have been known to include D6G, S149I, G144fs, and Y137C amino acid changes in addition to a c.115C>T exon 2 deletion.
