Inflammation clashing onto myocardial susceptibility: a tale of two rare diseases-a case report.

Background: Sarcoidosis is a rare inflammatory disease characterized by the presence of myocardial non-caseating granulomas. Heart failure, conduction abnormalities, and/or life-threatening arrhythmias are the main manifestations of cardiac sarcoidosis (CS). Cardiac magnetic resonance plays a major role in the diagnostic suspicion of cardiac involvement in sarcoidosis. However, late gadolinium enhancement (LGE) patterns are non-specific, and one should consider alternative or additional aetiologies for myocardial disease. Case summary: We report the case of a 40-year-old male with a past medical history remarkable for pulmonary and cutaneous sarcoidosis, presenting with asymptomatic premature ventricular contractions and severe left ventricular (LV) dilation and moderately reduced systolic function. Computed tomography angiography excluded coronary artery disease. Cardiac magnetic resonance revealed myocardial oedema in the anterior, anterolateral, and inferolateral walls and the presence of septal intra-mural and anterior, inferior, and lateral sub-epicardial 'ring-like' LGE. He had elevated inflammatory plasma biomarkers. N-terminal pro-brain natriuretic peptide was 110 pg/mL, and high-sensitivity troponin T was 20 ng/dL. Positron emission tomography computed tomography scan showed increased myocardial uptake consistent with inflammatory disease. Endomyocardial biopsy was normal. Thus, a presumptive diagnosis of isolated CS was made, and immunosuppression therapy was initiated, with full LV function recovery. Given the 'ring-like' LGE pattern, we recommended genetic testing, which identified a deletion in the dystrophin gene, classified as likely pathogenic. Discussion: This case highlights the contemporary diagnostic pathway for primary cardiomyopathies, emphasizing the increased likelihood of genetically influenced myocardial vulnerability to continuous harm when coupled with an acquired precipitant of myocardial damage. We describe a case of CS likely superimposed on a genetic myocardial substrate.