Motor neuron disease in a patient with a mitochondrial tRNAIIe mutation

Objective: Motor neuron disease (MND) is a common neurodegenerative condition for which the underlying cause is uncertain in many patients. We identified a patient with clinical features suggestive of MND but additional cardiac and metabolic symptoms. We wished to determine if the clinical features were due to a mitochondrial DNA mutation. Methods: The brain and spinal cord were studied using neuropathological techniques and agenetic defect investigated in individual neurons. Results: There were atypical neuropathological features and genetic studies identified a pathogenic, heteroplasmic mitochondria tRNA(11c) (4274T > C) mutation. Interpretation. This case adds to the phenotypic variation seen in mitochondrial DNA disease but also highlights the potential role of mitochondrial dysfunction in the cause of MND.