Myasthenia gravis and D-penicillamine.

There has been some uncertainty as to whether the apparent association between myasthenia gravis (MG) and D-penicillamine (D-P)-treated rheumatoid arthritis (RA) could be due to chance or whether the drug is responsible. In the absence of D-P, RA is found in association with MG, but this may simply reflect the high prevalence of RA. Although MG may be more common than expected after D-P treatment of RA, it probably occurs in only approximately 1% of such patients. In these circumstances, it is difficult to prove that D-P can induce MG, but compelling evidence in support for this possibility comes from the finding of differences between autoantibodies when spontaneous and D-P-associated MG are compared. These serologic differences could be explained in terms of an effect of D-P on antigen presentation and/or immunoregulation.