Long-term remission is rare in patients with myasthenia gravis (MG), and health-related quality of life is lower in patients with MG than in healthy individuals. Approximately 5% of patients with MG show positive results on muscle-specific kinase (MuSK) antibody testing and usually have severe symptoms, refractory disease, residual muscle atrophy, and poor prognosis. Recent studies that have investigated the pathogenesis of MuSK antibody-positive MG have reported contributors to treatment refractoriness in cases of MG. In this article, we review the most recent findings.