PT - JOURNAL ARTICLE AU - Nuno Moura-Coelho AU - Rita Pinto Proença AU - Joana Tavares Ferreira AU - João Paulo Cunha TI - Late-onset Leber’s hereditary optic neuropathy: the role of environmental factors in hereditary diseases AID - 10.1136/bcr-2018-227977 DP - 2019 Mar 01 TA - BMJ Case Reports PG - e227977 VI - 12 IP - 3 4099 - http://casereports.bmj.com/content/12/3/e227977.short 4100 - http://casereports.bmj.com/content/12/3/e227977.full SO - BMJ Case Reports2019 Mar 01; 12 AB - Leber’s hereditary optic neuropathy (LHON) is an optic neuropathy of mitochondrial inheritance, characterised by incomplete penetrance and variable expressivity. Typically, young male patients present with sequential, severe, rapidly progressive loss of central vision, with characteristic funduscopic findings. However, LHON may present at any age, in both genders, and fundus examination may be normal. Evidence has emerged to support the role of environmental factors in triggering LHON, by disrupting the normal mechanisms of mitochondrial function. We present two clinical cases of LHON of late onset, and provide a literature review on atypical cases of LHON and the role of environmental triggers.