Related Experiment Videos
Respiratory chain complex-I defect mimicking myasthenia
J Finsterer1, I Oberman, A Reitner
1Ludwig Boltzmann Institute for Research in Epilepsy and Neuromuscular Disorders, Vienna, Austria.
Metabolic Brain Disease
|March 15, 2002
Summary
Respiratory chain disorders, specifically complex-I defects, can mimic ocular myasthenia. This condition may present with similar symptoms and electrophysiological findings, leading to misdiagnosis and ineffective initial treatments.
Area of Science:
- Neurology
- Biochemistry
- Muscle Physiology
Background:
- Ocular myasthenia gravis is an autoimmune disorder affecting neuromuscular junctions, typically diagnosed via clinical signs, Tensilon tests, and acetylcholine-receptor antibodies.
- Repetitive nerve stimulation can reveal abnormalities in neuromuscular transmission, aiding in myasthenia diagnosis.
Observation:
- A 67-year-old woman presented with ptosis, diplopia, and dysphagia, initially suspected as ocular myasthenia.
- She showed ambiguous Tensilon tests, normal acetylcholine-receptor antibodies, and abnormal low-frequency repetitive stimulation responses.
- Pyridostigmine was ineffective, but corticosteroids provided temporary improvement, followed by lower-limb weakness.
Findings:
- Reevaluation revealed elevated serum lactate during exercise, myogenic electromyography, ragged-red fibers, and abnormal mitochondria on muscle biopsy.
- Biochemical analysis identified a respiratory chain complex-I defect.
- The patient was diagnosed with a respiratory chain disorder mimicking ocular myasthenia.
Implications:
- Respiratory chain disorders, particularly complex-I defects, can present clinically and electrophysiologically similar to ocular myasthenia.
- These mitochondrial disorders may respond transiently to treatments like corticosteroids, complicating diagnosis.
- Accurate diagnosis requires comprehensive investigation including metabolic and muscle biopsy studies to differentiate from autoimmune neuromuscular disorders.