Giant cell myocarditis attributable to myositis: therapeutic management under the guidance of serial endomyocardial biopsy—a case report

Giant cell myocarditis is a fatal disease that could be rapidly progressive if not properly managed. However, the role of immunosuppressive therapy, especially in refractory cases, remains unclear.

A 76-year-old man presented with back pain with elevated cardiac enzymes. Skeletal muscle and endomyocardial biopsies revealed giant cell myositis and giant cell myocarditis. Despite the initial immunosuppressive therapy, cardiac enzymes continued to rise. Serial endomyocardial biopsies enabled combination treatment of prednisolone, cyclosporine, and mycophenolate mofetil according to histological inflammatory activity.

We presented a case of refractory giant cell myocarditis preceded by giant cell myositis. While endomyocardial biopsy is an approach with risk of procedural complications, it can guide giant cell myocarditis management when the initial immunosuppressive therapy is ineffective.