Co-occurrence of m.1555A>G and m.11778G>A mitochondrial DNA mutations in two Indian families with strikingly different clinical penetrance of Leber hereditary optic neuropathy

Background Mitochondrial DNA (mtDNA) mutations are known to cause Leber hereditary optic neuropathy (LHON). However, the co-occurrence of double pathogenic mutations with different pathological significance in pedigrees is a rare event.