Coexistence of autoimmune diseases and autoantibodies in patients with myasthenia gravis.

Background: In this study, we assessed 75 patients with myasthenia gravis (MG) for coexistent autoimmune diseases (ADs) and for the characteristic autoantibodies that are associated with the most relevant forms of ADs.

Methods: The demographic and clinical characteristics of the patients were recorded. In all patients, thyroid function tests, thyroid autoantibodies, and other autoantibodies were studied. The diagnosis of autoimmune thyroid disease (AITD) was made based on the clinical features, physical examination, and laboratory findings. The diagnoses of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) were made in accordance with the revised criteria of American College of Rheumatology. The presence of other ADs were also recorded which was based on whether or not the patient already had a diagnosis of ADs; or, whether it was detected during the period of the study based on clinical findings and/or laboratory abnormalities.

Results: Thirty-nine patients (52%) had autoantibody positivity in their sera. Thyroid autoantibodies and antinuclear antibodies were the main autoantibodies detected. In twenty one of these patients, a diagnosis of AD could not be confirmed. Eighteen patients (24%) had a confirmed diagnosis of a coexisting AD. These ADs included AITD (16%), RA (4%), SLE (2.6%), and Lambert-Eaton myasthenic syndrome (1.3%). In ten patients, the diagnosis of ADs had been established before the development of MG; 8 of the patients included those who were newly diagnosed with ADs in the course of the management of MG.

Conclusions: MG has an increased frequency of coexisting ADs. Autoantibodies that are characteristic for ADs can be found in the patients without the presence of any of the clinical findings of ADs. Clinical attention towards the management of ADs is especially needed during the follow-up of patients with MG.