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Introduction Iron deposition in internal organs in hemochromatosis patients assessed by cardiac magnetic resonance (CMR) is associated with fibrosis. Moreover, experimental data show that iron accumulation promotes lung, kidney and heart fibrosis, probably through induction of oxidative stress and subsequent mesenchymal transition of tissue-resident cells towards myofibroblasts (Life 2022;12:430, Nat Metab 2023;12:2111-30). Microvasculopathy-related extravasation of erythrocytes that store 70% of total body iron, as depicted by capillaroscopy in SSc, may lead to local tissue iron deposition. Thus, we hypothesized that CMR may reveal myocardial iron deposition in SSc patients with primary heart disease.Material and Methods SSc patients with clinically suspected primary heart disease, based on symptoms, increased serum troponin and/or proBNP, and/or abnormal 24h ECG monitoring and/or echocardiography underwent CMR imaging using a 3T Vida, Siemens scanner. Their CMR results were compared with CMR from, a) acute myocarditis without autoimmune rheumatic disease (ARD), b) cardiac involvement, due to other than SSc ARDs and c) healthy controls. T1, T2, T2* mapping images were assessed in basal, mid and apical area of left ventricle (LV) and the above parameters were calculated in interventricular septum, anterior, lateral and inferior wall of LV. For each segment, native T1 mapping and myocardial extracellular volume fraction (ECV) indicative of diffuse fibrosis, T2 mapping indicative of oedema and T2* mapping indicative of iron deposition were measured.Results Increased T1 mapping, ECV and T2 mapping values were found in 29/34 SSc patients, suggestive of primary heart disease. Iron deposition detected by decreased T2* values in at least one myocardial segment, was evident in 21/34 SSc patients and in 4/5 patients with other ARDs, versus 0/20 patients with acute myocarditis and 0/8 healthy controls. No segmental predilection for myocardial iron deposition was observed in SSc. Comparison of segments with or without iron deposition did not show differences regarding local coexistence of either oedema (12,4% vs. 18,1%, respectively) or diffuse fibrosis (77,5% vs. 80.8%, respectively). However, among myocardial segments with iron deposition, the presence of fibrosis was more frequent compared to oedema (77% vs. 12%, p<0.001). Repetitive CMR after one year was performed in 6 patients showing new iron deposition in 3, regression in 2 and no change in one patient.Conclusions Myocardial iron deposition is a common finding in SSc patients with suspected primary heart disease and may denote local microvasculopathy. Additional studies to explore the pathogenic role of iron deposition in tissue fibrosis in SSc are underway.