Successful treatment of fulminant and recurrent lymphocytic myocarditis with calcineurin inhibitors

Abstract Lymphocytic myocarditis (LM) is primarily triggered by various factors including viral infections and subsequent immune responses. While rare, some patients with LM experience recurrence with a life‐threatening fulminant form. Although combining steroids and immunosuppressants, such as azathioprine and mycophenolate mofetil, has demonstrated favourable outcomes in patients with LM, their efficacy is limited to the chronic phase. Indeed, various immunosuppressants have been used for LM with fulminant manifestation; however, their evidence remains lacking. In our case series, two patients with LM experienced fulminant relapses during steroid tapering, and another presented persistent cardiac enzymes elevation despite steroid therapies. Consequently, we initiated calcineurin inhibitors alongside steroids, resulting in well‐controlled clinical courses without further recurrence of LM and significant adverse effects. Our cases suggest calcineurin inhibitors as therapeutic options for managing steroid‐resistant LM with fulminant relapse.