The neurogenic weakness, ataxia and retinitis pigmentosa (NARP) syndrome mtDNA mutation (T8993G) triggers muscle ATPase deficiency and hypocitrullinaemia

Based on the study of three unrelated families, we report what we believe to be the first in vivo evidence of muscle ATPase deficiency in individuals carrying the neurogenic weakness, ataxia and retinitis pigmentosa (NARP) syndrome mtDNA mutation (T8993G). Since plasma citrulline was consistently low in 4/5 patients, we suggest that the NARP mutation caused complex V deficiency in the small intestine as well, thus reducing the availability of mitochondrial ATP required for citrulline synthesis.