Diplopia as the herald of fulminant myocarditis in undifferentiated connective tissue disease: a case report

This manuscript describes a rare case of undifferentiated connective tissue disease (UCTD)-associated fulminant myocarditis presenting with isolated diplopia as the sole initial manifestation. A 66-year-old Chinese woman presented with a 17-day history of isolated diplopia. Initial evaluation revealed markedly elevated cardiac enzyme profile and electrocardiographic changes suggestive of acute myocardial infarction. However, coronary angiography revealed no coronary stenosis. Cardiac magnetic resonance imaging (MRI) was consistent with myocarditis. The initial diagnoses included Miller-Fisher syndrome and inflammatory cardiomyopathy. The patient underwent plasma exchange, intravenous methylprednisolone (20 mg daily), and intravenous immunoglobulin (IVIg). Her condition improved. After discharge, oral prednisone was initiated at 20 mg daily, with a weekly taper of 5 mg. However, 12 days after discharge, she was readmitted with abdominal distension. At that time, she also presented with hypotension and ophthalmoplegia. Brain MRI revealed abnormal signals in the medial and lateral rectus muscles bilaterally. Echocardiography revealed a reduced left ventricular ejection fraction (LVEF) of 38%. Endomyocardial biopsy confirmed lymphocytic myocarditis, and serology was positive for anti-SSA/Ro52 antibodies and borderline positive for anti-PL-7 antibody, leading to a diagnosis of UCTD-associated fulminant myocarditis. Treatment with methylprednisolone (60 mg daily) and IVIg resulted in clinical recovery. At three-year follow-up, the patient remained in remission, with complete resolution of diplopia, normalization of cardiac enzyme profile, and no progression to any definite connective tissue disease. This case suggests that isolated diplopia as the sole initial manifestation of UCTD-associated fulminant myocarditis is exceedingly rare. For autoimmune myocarditis, endomyocardial biopsy is crucial to guide treatment. Premature tapering of low-dose corticosteroids led to rapid relapse, highlighting the importance of starting with an adequate dose, tapering slowly, and maintaining the minimal effective dose.