A 55-year-old male patient with diffuse cutaneous systemic sclerosis (dcSSC) since 2018 presented with a history of arrhythmia. He had been stable for 5 years with pantoprazole, diltiazem, and mycophenolate mofetil (MMF)
vitamin E
and vitamin D until he developed arrhythmia. Different evaluations revealed left bundle branch block, wall motion abnormality, mildly reduced systolic function, diffused interstitial fibrosis, and lesions in the left circumflex artery (LCX) and left anterior descending artery (LAD) and stenosis in LCX, without significant improvement following percutaneous coronary intervention for LCX stenosis. Holter monitoring demonstrated persistent ventricular premature beats and couplets. Arrhythmia was not responsive to bisoprolol therapy, and it was not feasible to perform cardiac ablation. Suspecting MMF-induced arrhythmia, MMF was discontinued, which led to a reduction in arrhythmia and symptom improvement after 9 months. This case report emphasized a possible heart-related complication of MMF, which healthcare providers should consider when prescribing medication to patients.