Genetic Landscape of Patients With Dilated Cardiomyopathy and a Systemic Immune-Mediated Disease

BACKGROUND: Systemic immune-mediated diseases (SIDs) are a well-known cause of dilated cardiomyopathy (DCM), a cardiac phenotype influenced by genetic predispositions and environmental factors. OBJECTIVES: This study sought to examine if an underlying genetic predisposition is present in patients with DCM and SID. METHODS: Genotyped DCM-SID patients (n = 183) were enrolled at 3 European centers. Genetic variants were compared with healthy control subjects (n = 20,917), DCM patients without SID (n = 560), and individuals with a suspicion of an SID (n = 1,333). Clinical outcomes included all-cause mortality, heart failure hospitalization, and life-threatening arrhythmias. RESULTS: The SID diagnosis preceded the DCM diagnosis by 4.8 months (Q1-Q3: -68.4 to +2.4 months). The prevalence of pathogenic/likely pathogenic (P/LP) variants in DCM patients with an SID from the Maastricht cohort was 17.1%, compared with 1.9% in healthy control subjects (P < 0.001). In the Madrid/Trieste cohort, the prevalence was 20.5% (P < 0.001). Truncating variants showed the strongest enrichment (10.7% [OR: 24.5] (Maastricht) and 16% [OR: 116.6 (Madrid/Trieste); both P < 0.001), with truncating TTN (titin) variant (TTNtv) being the most prevalent. Left ventricular ejection fraction at presentation was reduced in TTNtv-SID patients compared with DCM patients with SID without a P/LP (P = 0.016). The presence of a P/LP variant in DCM-SID had no impact on clinical outcomes over a median follow-up of 8.4 years (Q1-Q3: 4.9-12.1 years). CONCLUSIONS: One in 6 DCM patients with an SID has an underlying P/LP variant in a DCM-associated gene. This highlights the role of genetic testing in those patients with immune-mediated DCM, and supports the concept that autoimmunity may play a role in unveiling a DCM phenotype in genotype-positive individuals.