Beyond what the eye can see.

A 45-year-old woman presented with acute sequential optic neuropathy resulting in bilateral complete blindness. No significant visual recovery occurred. Past medical history was relevant for severe preeclampsia with resultant renal failure, diabetes mellitus, and sudden bilateral hearing loss when she was 38 years old. There was a family history of diabetes mellitus in her mother. Testing for common causes of bilateral optic neuropathy did not reveal a diagnosis for her illness. The maternal and personal history of diabetes and deafness prompted testing for mitochondrial disease. The 3 primary mitochondrial DNA mutations responsible for Leber hereditary optic neuropathy were absent, but the patient was subsequently found to have a disease causing mitochondrial DNA mutation, m.13513G>A. The case illustrates the importance of early testing for mitochondrial disease and demonstrates that Leber hereditary optic neuropathy-like presentations may be missed if testing is limited to the 3 primary mutations.