Cardiac magnetic resonance in a rare case of recurrent mesalazine-induced myocarditis

Mesalazine represents a key treatment for intestinal bowel diseases and only in rare cases produces cardiac toxicity, with a not completely known mechanism. We report a case of a 25-year-old man with a first episode of myocarditis after 2 weeks from the first mesalazine intake, documented also by a characteristic cardiac magnetic resonance pattern. Then, after less than 1 month, he suffered myocarditis recurrence and so, guided by a multidisciplinary team evaluation, in the suspicion of mesalazine-induced myocarditis, the drug was promptly stopped, with consequent recovery of cardiac damage. In our patient, the recurrence of myocarditis because of the non-interruption of the drug is very peculiar (only three cases described in literature) and definitively confirms the diagnosis. Plain language summary: This paper reports an exemplary case of cardiac toxicity induced by mesalazine, a key treatment for inflammatory bowel diseases such as Crohn's disease and ulcerative colitis. In rare cases, this drug can lead to cardiac impairment, with a mechanism not yet clarified. The young patient described experiencing a first episode of myocarditis (inflammation of the heart muscle cells) after 2 weeks of starting mesalazine. The diagnosis was possible thanks to cardiac magnetic resonance, a noninvasive exam providing high-definition images associated with tissue characterization. Mesalazine was not discontinued because drug-induced etiology was not suspected, due to its rarity. Consequently, the patient suffered a second episode of myocarditis, diagnosed by endomyocardial biopsy, an invasive technique that can accurately assess the etiology of myocardial damage, leading to prompt cessation of treatment. Since myocarditis can have various causes, diagnosis was also facilitated through a multidisciplinary team, which ruled out other possible causes for this condition. This case report is highly educational and underscores the importance of clinicians being vigilant about this side effect and considering it in patients taking mesalazine who present with myocarditis, to promptly discontinue the treatment. Mesalazine interruption is otherwise the only effective therapy for this condition, in addition to anti-inflammatory and analgesic drugs. Furthermore, this paper highlights the increasing importance of multidisciplinary teams, comprising various specialists, for accurate diagnosis and therapeutic decisions. The authors also propose an algorithm for diagnosing mesalazine-induced myocarditis, with certainty derived from recurrence after drug rechallenge, either voluntarily or accidentally, as demonstrated in this case.