title: Respiratory chain complex-I defect mimicking myasthenia.
abstract: In a 67-year-old woman with ptosis, double vision, dysphagia, ambiguous Tensilon tests, normal acetylcholine-receptor antibodies, normal thymus, and repeatedly abnormal responses to low-frequency repetitive stimulation, ocular myasthenia was suspected. Pyridostigmin was ineffective, but corticosteroids improved the abnormalities. Despite this therapy, lower-limb weakness developed. Reevaluation disclosed abnormal increase of serum lactate during slight exercise, myogenic electromyography, ragged-red fibers, reduced oxidative enzyme staining and abnormally shaped and structured mitochondria on muscle biopsy, and a respiratory chain complex-I defect on biochemical investigation of the muscle homogenate. Respiratory chain disorder due to complex-I defect with abnormal decremental response to low-frequency repetitive stimulation was diagnosed. It is concluded that respiratory chain disorders due to a complex-I defect may mimic ocular myasthenia clinically, electrophysiologically, and even therapeutically.
authors.affiliation: Ludwig Boltzmann Institute for Research in Epilepsy and Neuromuscular Disorders, Vienna, Austria.
authors.forename: J
authors.initials: J
authors.lastname: Finsterer
authors.forename: I
authors.initials: I
authors.lastname: Oberman
authors.forename: A
authors.initials: A
authors.lastname: Reitner
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000368:Aged; D001763:Blepharoptosis / Q000209:etiology; D003937:Diagnosis, Differential; D004172:Diplopia / Q000188:drug therapy / Q000209:etiology; D004558:Electric Stimulation; D004576:Electromyography; D004579:Electron Transport / Q000235:genetics*; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008661:Metabolism, Inborn Errors / Q000175:diagnosis* / Q000188:drug therapy / Q000235:genetics*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D009157:Myasthenia Gravis / Q000175:diagnosis*; D009886:Ophthalmoplegia / Q000188:drug therapy / Q000209:etiology
chemical_list: D000305:Adrenal Cortex Hormones