Coexistence of systemic lupus erythematosus and myasthenia gravis: two distinct populations of anti-DNA and anti-acetylcholine receptor antibodies.

A woman with a four-year history of systemic lupus erythematosus (SLE) developed myasthenia gravis (MG). The clinical features of lupus disappeared slowly while the myasthenic syndrome became predominant. However, her serum was positive for anti-DNA and anti-acetylcholine receptor antibodies. Cross-reactivity between anti-DNA antibodies and anti-acetylcholine receptor antibodies was not demonstrated, suggesting the presence of two different populations. A cellular immunology profile was normal as expected in MG and in contrast to SLE. Conceivably, SLE and MG might represent two opposite extremes in the spectrum of autoimmune diseases.