D ‐penicillamine‐associated myasthenia gravis: Immunological and electrophysiological studies

Immunological and electrophysiological features were investigated in a patient with rheumatoid arthritis who developed myasthenic symptoms after 10 months of treatment with D ‐penicillamine ( D ‐pen). After an initial rise, acetylcholine receptor (AChR) antibodies gradually fell from 24.4 nmole α‐bungarotoxin bound/liter to 1.8 nmole/liter following withdrawal of the drug, and this was associated with clinical and electrophysiological improvement. Immunoglobulin synthesis by peripheral blood lymphocytes cultured with pokeweed mitogen and D ‐pen was significantly increased at D ‐pen concentrations of 10–100 μg/ml in 2 patients with D ‐pen associated myasthenia gravis and 1 out of 3 normal individuals. Furthermore, lymphocytes from 1 myasthenic patient synthesized detactable AChR antibodies in vitro, and the amount of receptor antibody produced was increased in the presence of the drug. This effect was most marked at a concentration of 10 μg/ml which is thought to approximate the concentration in vivo. Our results confirm the in vivo findings of others that D ‐pen may have different effects on immunoglobulin production in different individuals and may also enhance the synthesis of at least 1 autoantibody, the AChR antibody.