The mitochondrial genetic background is known to influence the expression of the optic atrophy: i.e the LHON mitochondrial primary mutations G11778A and T14484C showed significant clustering on Caucasian mtDNA haplogroup J. It has been suggested that this clustering result from an accumulation of non-synonymous J polymorphisms on the cytochrome b gene G15257A, T14798C [18]. The gene discussed is MT-CYB; the disease is hereditary optic atrophy.