Myasthenia gravis-associated systemic vasculitis and myocarditis with involvement of the cardiac conducting tissue

We describe unexpected autopsy findings in an elderly woman with myasthenia gravis (MG) who had myocarditis of the working and conducting myocardium and coronary and renal vasculitis. Myasthenia gravis, characterized by autoantibodies to the acetylcholine receptor in the postsynaptic cell membrane, may be associated with other autoimmune disorders. An additional manifestation of autoimmunity is the presence of heart muscle antibodies, which may be the basis for myocarditis, which has been reported in up to 60% of MG patients at autopsy. Although myocarditis of the working myocardium is rather common, conduction system myocarditis and systemic vasculitis have not been previously reported in MG.