Abstract

Background: Myasthenia gravis (MG) is an autoimmune disorder of neuromuscular transmission. The majority of patients show abnormal thymic histology.

Setting: The study was performed at the Myasthenia Gravis Center, Karolinska University Hospital and at the Immunological Research Laboratory, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden.

Patients and Methods Information was collected retrospectively since 1956 and prospectively since 1975 concerning the clinical data, concomitant diseases, concentration of serum acetylcholine receptor antibodies (AChR-ab), the immunosuppressive treatment (IS) and the response to it in 537 patients of whom 326 were thymectomized. The follow-up time was 1.5-50 years.

Results: The age at onset of MG was increasing from a median age of 24 years before 1975 to a median age of 61 years after 2000. Thymoma was found in 65, hyperplasia (HPL) in 185 and normal thymus in 76 patients. The transsternal surgical approach for thymectomy was used in 255 patients (78%). In five patients with thymoma MG appeared after the thymectomy. Out of 537 patients 466 (87 %) had circulating AChR-abs. IS was given to 300 (56%) patients, mostly used in patients with thymoma (85%). Totally, 441 patients (82%) improved. One third of the patients with HPL-, one fourth of those with thymoma, one fifth of those with a normal thymus- and one seventh of not operated patients, went into remission.

Conclusion: The prognosis for the majority of patients with MG is favorable irrespective of thymic histology. The cause may be the use of immunomodulating therapy.