Fast Five Quiz: Pathophysiology of Myasthenia Gravis

Raghav Govindarajan, MD; Nicholas J. Silvestri, MD


September 15, 2023

One of the most critical distinctions between the immunopathology of MuSK and AChR MG is the role of the thymus. Many studies focus on B cells located in the medulla; however, a second body of B cells is also present in non-epithelial perivascular spaces of the thymus. The thymus of patients with MG contains activated B cells and plasma cells specific for AChR; however, abnormal thymus histopathologic findings are not observed in patients with MuSK MG. Approximately 60%-80% of patients with MG develop thymic follicular hyperplasia in which the normal thymic lymphoepithelial architecture is disrupted and replaced by B-cell follicles that generate plasma cells. Thymic pathology primarily occurs in females, peaking between the ages of 20 and 40 years. Thymectomy with proper cortisone therapy has been shown to reduce the concentration of AChR antibodies with continuous regression in patients with early-onset AChR MG.

AChR MG can be further divided into subtypes on the basis of age of disease onset and sex. Patients who develop the disease before the age of 50 years via early-onset MG are often females. Patients who develop the disease after the age of 50 years are diagnosed with late-onset MG and are more often males.

Learn more about the pathophysiology of MG.


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