Optic neuropathy with or without other features is a common cause of referral to mitochondrial specialists, and can pose a diagnostic challenge. Whereas isolated optic neuropathies in and of themselves are devastating enough, those associated with broader mitochondrial diseases can herald a multi-organ progressive disorder.
Angebault et al (AJHG 2015 (97) 754-760) described a new gene for isolated and syndromic optic neuropathy: RTN4IP1. This gene encodes a mitochondrial ubiquinol oxydo-reductase, and fibroblasts from affected individuals have evidence of complex I and IV deficiencies. Affected patients have features ranging from isolated optic neuropathy to a cerebellar syndrome with intellectual disabilities. While only a few patients have been identified to date, the phenotypic spectrum will likely expand as more individuals are identified.
Hilary Vernon, MD PhD