Late-Onset Myasthenia Gravis in a Patient with Recurrent Breast Cancer: A Case Report

Abstract

Introduction: Myasthenia gravis (MG) is an autoimmune disorder characterized by fatigable weakness, typically affecting voluntary muscles. Myasthenia gravis as a paraneoplastic syndrome (PNS) of a thymoma is well known, but it is rare to have MG PNS due to extrathymic neoplasms. Case: We present a case on an 80-year-old female who was diagnosed with myasthenia gravis in the presence of recurrent metastatic breast cancer. Discussion: The question remains whether MG is truly a neoplastic syndrome of breast cancer, or if older individuals are more likely to suffer from both breast cancer and late-onset myasthenia gravis (LOMG) at the same time. It was found that those diagnosed with LOMG are more likely to have extrathymic neoplasms. Regardless, the underlying malignancy should be treated, MG treatment should be initiated, and if PNS is suspected immunosuppressants are indicated. Conclusion: This case highlights the complexity of classifying MG in elderly patients with a concomitant neoplasm, but nonetheless, MG as a PNS of breast cancer remains a possibility.