Neuromuscular transmission in rheumatoid arthritis, with and without penicillamine treatment

Electroneuromyographic studies were performed on patients with rheumatoid arthritis, some of whom were received penicillamine, to determine whether a subclinical defect of neuromuscular transmission existed. There were no significant differences between patients and controls with respect to nerve conduction studies or repetitive ulnar nerve stimulation. Four patients (three receiving penicillamine) demonstrated mild neurogenic changes distally on needle electromyography. Mean jitter was slightly higher for patients receiving penicillamine than in other patients or controls, but the differences were not significant. No significant correlations existed between of the studies and daily, cumulative, or average penicillamine dosage. A significant positive correlation (p less than 0.001) existed between jitter and duration of disease in patients receiving penicillamine. Results were consistent with the hypothesis that penicillamine predisposes certain individuals to develop myasthenia gravis rather than interfering directly with neuromuscular transmission.