[A case of anti-MuSK positive MG with recurrent right-sided heart failure as the initial manifestation].

We report a case of anti-MuSK antibody (Ab)-positive myasthenia gravis (MG) in a patient who developed recurrent right-sided congestive heart failure. The patient presented with right-sided congestive heart failure of unknown etiology, necessitating hospitalization on three occasions over a 6-month period. During the third episode of hospitalization, she developed disturbance of consciousness, and heart failure was attributed to carbon dioxide narcosis. We performed various investigations including an anti-MuSK Ab assay, which showed positive results, and she was diagnosed with MG based solely on anti-MuSK Ab positivity. Selective plasma exchange did not produce a satisfactory therapeutic effect, and she received additional intravenous immunoglobulin, plasmapheresis, and oral immunosuppressive therapy after which she was successfully weaned off the ventilator. This case report highlights the following points: (a) Recurrent right-sided congestive heart failure may be the first manifestation of anti-MuSK Ab-positive MG and, (b) detection of the anti-MuSK Ab alone is a convincing rationale to diagnose patients with MG.