Fulminant lymphocytic myocarditis with unusual giant cell detection: a case report.

Background: An accurate and rapid pathologic diagnostic in fulminant myocarditis is crucial for appropriate therapeutic decision-making. Since giant cells can appear in various conditions, careful judgment based on repeated imaging, pathological analysis, and close clinical follow-up is essential to make precise decisions.

Case Summary: A previously healthy 36-year-old woman was admitted to the hospital with haemodynamic compromise requiring mechanical circulatory support. Pathologic findings of left ventricular (LV) at the time of left ventricular assist device (LVAD) implantation confirmed the diagnosis of lymphocytic myocarditis. Cardiac function had gradually recovered, and LVAD was successfully weaned on post-operative day (POD) 10. However, surgical biopsy of LV at the time of LVAD removal revealed multinucleated giant cell formation, resulting in administered prednisolone for 2 weeks. After the withdrawal of prednisolone, pathologic findings of the right ventricle (RV) endomyocardial biopsy (EMB) specimens obtained on POD 21 showed continuous resolving myocarditis without any giant cell formation. Several additional examinations showed no evidence of an autoimmune-related disease background. The cardiac catheterisation performed on POD 85 showed normal hemodynamics with preserved LV function and EMB of the RV showed resolving myocarditis without giant cells. One year later, the patient was well without immunosuppressive therapy.

Discussion: The multinucleated giant cell formation might be the accidental result of the fusion of macrophages that had ingested myocardial calcifications or degenerative macromolecules formed by the severe inflammatory process of lymphocytic myocarditis. The massive calcium deposition in both ventricles on CT and the positivity of monocytic markers in giant cells support this hypothesis.