Igg4- related disease masquerading as culture-negative endocarditis

We detail an extremely rare case of noninfective endocarditis secondary to IgG4-related disease on the mitral valve. A 75-year-old-woman with mitral valve ring annuloplasty presented with subacute, intermittent, self-limiting neurologic deficits. Magnetic resonance imaging of her brain revealed multiple small infarcts consistent with a cardioembolic phenomenon. Transesophageal echocardiogram revealed mobile, strand-like vegetations. She was taken for surgical repair of her mitral valve and tissue biopsy confirmed the diagnosis of IgG4-related disease. Our knowledge of this rare disease is continuously evolving, and this case highlights an exceptionally rare manifestation of this poorly understood disease.