Progressive mitochondrial disease resulting from a novel missense mutationin the mitochondrial DNA ND3 gene

We describe a 42-year-old man who presented with a progressive history of e pilepsy, stroke-like episodes, bilateral optic atrophy, and cognitive decli ne. Investigation of his muscle biopsy revealed a specific defect in comple x I activity. Subsequent analysis of the mitochondria genome identified a n ovel heteroplasmic T10191C mutation in the ND3 gene. The mutation was prese nt at Lower levels in blood from the patient and unaffected maternal relati ves and is the first pathogenic mitochondria DNA mutation in the ND3 gene t o be described.