This case shows that although mesalazine is considered the primary treatment for IBD, it can have rare but serious side effects, including myocarditis, which can worsen over time with complications such as heart block, LV failure, dilated cardiomyopathy, cardiac arrest, and tachyarrhythmias [10]. The underlying mechanisms causing mesalazine-associated myocarditis include IgE-mediated allergic reactions, direct cardiac toxicity, cell-mediated hypersensitivity, or a humoral antibody response against 5-ASA derivatives [29]. The gene discussed is IGHE; the disease is myocarditis.