Case Presentation: Cardiac manifestations of dermatomyositis (DM) are under-recognized and can significantly increase morbidity and mortality through the development of arrhythmias, heart failure, and myocarditis. We report a 24-year-old male with no prior cardiovascular history who presented with three months of progressive fatigue, malaise, weight gain, and difficulty rising from a seated position. Examination revealed heliotrope rash, periungual erythema, and proximal muscle weakness. Laboratory evaluation showed moderately elevated inflammatory markers and cardiac enzymes. Thigh MRI showed increased T2 signal and subsequent biopsy confirmed DM with perifascicular atrophy and perivascular inflammation. To investigate the elevated cardiac enzyme level, invasive coronary angiography was performed and revealed nonobstructive coronary disease, while transthoracic echocardiogram (TTE) showed preserved systolic and diastolic function. Subsequent cardiac MRI (CMR) demonstrated subepicardial and periepicardial enhancement and mid-anterolateral wall scarring, consistent with myopericarditis. Notably, over the subsequent clinical course, cardiac troponin levels increased during dermatomyositis flares and decreased when symptoms were well controlled. In the absence of other clear triggers for myocarditis (such as recent viral infection) and with improvement in cardiac enzymes with immunosuppressive therapy, a diagnosis of dermatomyositis-associated myocarditis (DAM) was made. Escalation of his immunosuppressive therapy with corticosteroids, more frequent intravenous immunoglobulin (IVIG), and mycophenolate mofetil led to marked clinical improvement in muscle strength, inflammatory markers, and cardiac enzymes.
Discussion: Cardiac involvement occurs in up to 40% of DM patients and may present as myo(peri)carditis, heart failure, or arrhythmias. In fact, a study concluded that the 10-year risk of heart failure and atrial fibrillation was significantly higher in DM/polymyositis patients compared to matched controls. Myocarditis is a primary manifestation of DM that is often underdiagnosed, and cardiac biopsy findings typically mirror those seen in skeletal muscle – myocardial inflammation, fibrosis, and necrosis. In fact, autopsy reports of DM patients revealed active myocarditis or focal fibrosis in up to 50% of cases, diagnosing DAM post-mortem. CMR is the most sensitive, noninvasive test for characterizing myocardial tissue compared to TTE, coronary angiography, and biopsy. In this patient, recurrent troponin elevations and CMR abnormalities in the setting of dermatomyositis flares confirmed DAM. Treatment of DAM focuses on immunosuppression and management of underlying myopathy, with empirical use of high-dose glucocorticoids, often combined with methotrexate, azathioprine, mycophenolate mofetil, rituximab, or IVIG in refractory cases. CMR is a valuable tool for diagnosis and monitoring of myocardial inflammation, and improvement in imaging findings has been observed following immunosuppressive therapy.
Conclusions: This case underscores the utility of CMR in the evaluation of patients with inflammatory myopathies, where cardiac manifestations are common yet often nonspecific. Early detection using CMR and relevant biomarkers is critical, as immunosuppressive therapy can improve both clinical and imaging outcomes. Routine cardiac screening and prompt treatment are essential to optimize prognosis of DAM in patients with DM.