Thymic pathological examination of non-thymomatous myasthenia gravis patients: A pilot study for prediction of outcome.

Background: Myasthenia gravis (MG) is an autoimmune disorder characterized by weakness and fatigability of skeletal muscles. The aim of this study was to determine if pathological characteristics in non-thymomatous patients of MG would correlate with prognosis in a three year follow up.

Methods: Patients who had had their thymectomy at least three years prior to the study were selected from three hospitals and were followed for 3 years. Prognosis was assessed via a devised prognostic scoring system. A pathological exam of the specimen from the thymus was done using the following immunohistochemical markers: Bcl2, CD 3, CD 4, CD 5, CD 7, CD 10, CD 20cy, CD 23, CD 43, and Ki67.

Results: Fifteen patients fulfilled the inclusion criteria and had a complete follow-up. This included 3 males and 12 females with a mean age of 36.6 years at the start of the study. The dominant cell population was T lymphocytes. All T cells expressed CD 3, CD 43, CD 5, and Bcl-2. In 2 patients, CD 10 marker was positive in T cells. B cells were negative for activation marker CD 23, except for germinal center dendritic cells. Due to the limited number of patients in the study, the power of the study would not allow for an analysis to assess correlation between histopathological data and prognosis.

Conclusion: This pilot study was an attempt to discover any prognostic indices from the histopathological examination of the resected thymic tissue in the patients with myasthenia gravis.