Cardiac sarcoidosis is a form of inflammatory cardiomyopathy with clinically significant complications: cardiac conduction disturbances, ventricular arrhythmias, heart failure, and sudden cardiac death. Epidemiological data on cardiac sarcoidosis are scarce. A young female patient was admitted with suspected acute coronary syndrome (ACS). Her troponins were positive, and her electrocardiogram (ECG) showed abnormal Q waves and ST segment elevation in the chest leads. A coronary angiography (CAG) was performed, and myocardial infarction (MI) was ruled out. Acute myocarditis was suspected, but the diagnosis was questionable due to the prolonged, severe course, multiple organ damage, and poor treatment response. Therefore, the patient was transferred to the Federal Center. At the Federal Center, magnetic resonance imaging (MRI), positron emission tomography combined with computed tomography (PET-CT), and myocardial biopsy were performed. The diagnosis was established two weeks after admission. Sarcoidosis is difficult to diagnose. Clinical suspicion of cardiac sarcoidosis arises in the following cases: First, there is a diagnosis of extracardiac sarcoidosis plus symptoms such as palpitations/dizziness/syncope, or signs such as ECG changes or cardiac imaging changes such as decreased left ventricular ejection fraction (LVEF), focal aneurysms/thinning of the basal septum. Second, when there is no evidence of extracardiac sarcoidosis, there are blocks (atrioventricular (AV) block, more than 2 degrees, type 2 in young people), and unexplained ventricular tachycardia (VT). The initial diagnostic workup requires: ECG; 24-hour ECG monitoring for palpitations, dizziness, or syncope; echocardiography (EchoCG), a normal EchoCG does not exclude cardiac sarcoidosis; exclusion of coronary artery disease (CAD) - CT angiography or invasive angiography if the area of ​​scar or perfusion/metabolic disorder does not correspond to nuclear imaging data.