Characterizing systemic lupus erythematosus associated myocarditis: From rare clinical disease to subclinical involvement.

OBJECTIVE: To define the frequency, clinical and subclinical spectrum, diagnostic findings, and outcomes of lupus-related myocarditis (LM) through a cohort study and systematic literature review (SLR). METHODS: We retrospectively analyzed LM cases cases from the AQUILES cohort (1990-2025), a tertiary-care systemic lupus erythematosus (SLE) registry (n = 534), and conducted a systematic literature review (SLR) from 1990 to February 2026. RESULTS: In the AQUILES cohort, 15/534 patients (2.8%) experienced 19 LM episodes. The SLR included 21 studies and 381 patients with sufficiently detailed data. The descriptive pooled frequency of LM was 1.7% (1.8% including our cohort); given study heterogeneity, these estimates should be interpreted cautiously. Studies using systematic cardiac magnetic resonance (CMR) assessment detected myocardial involvement in up to 46.9% of patients, with subclinical disease observed in 20% to 28.5%. These findings suggest that clinically overt LM captures only part of the myocardial inflammatory burden in SLE, although prospective follow-up data have not shown progression to clinically overt LM or clear prognostic implications. LM was the presenting manifestation of SLE in 45.1% of cases. It occurred predominantly in women (85.4%) in the third and fourth decades, usually in the setting of active multisystem disease, particularly lupus nephritis (61.6%), thrombocytopenia (45.7%), autoimmune hemolytic anemia (31.6%), and neuropsychiatric involvement (22.8%). The most common manifestations were dyspnea (67.9%), fever (52.6%), chest pain (33.5%), and palpitations (21.3%). Overall ECG abnormalities were observed in 33.3% of cases, reduced left ventricular ejection fraction (LVEF) on transthoracic echocardiography (TTE) in 63.4%, and CMR abnormalities compatible with myocarditis in 74.0%. Complete cardiac recovery was reported in 61.4% of patients, whereas 15.8% died. CONCLUSIONS: LM is an uncommon but severe manifestation of SLE, usually occurring in the context of active multisystem disease. CMR has expanded the recognized spectrum of lupus-related myocardial inflammation by identifying subclinical abnormalities, whose prognostic value and therapeutic implications remain uncertain. Clinically overt LM warrants early recognition and prompt treatment.