A 64-year-old man with rheumatoid arthritis (RA) presented to our emergency department with severe chest tightness and dyspnea. His electrocardiography (ECG) showed multiple premature atrial complexes (PACs) with wide QRS, and transthoracic echocardiography revealed severe hypokinesis of the left ventricle. The patient later developed sudden cardiovascular collapse with presumed fulminant myocarditis and cardiogenic shock. Further investigation showed that coronary angiogram, viral studies and autoimmune vasculitis markers were all negative. After high-dose intravenous immunoglobulin (IVIG) and systemic steroid were administered, a dramatic improvement of clinical conditionswas observed,with an increase of the left ventricular ejection fraction (LVEF) from10% to 42% within one week, and a resolution of the wide QRS on the ECG. The rapid recovery fromleft ventricular dysfunction by treatment with IVIG and systemic steroid suggests immunotherapy might be effective in RA patients with acute fulminant myocarditis.