Background: Rheumatoid arthritis (RA) may involve the cardiovascular system and can cause significant structural cardiac disease. RA mimicking infective endocarditis (IE) is rarely reported. Case summary: A 46-year-old man with a medical history of seropositive RA attended a planned outpatient visit for infliximab treatment. The pre-infusion examination revealed a pulse of 41 b.p.m. and the following electrocardiogram showed 3rd degree atrioventricular block. A temporary pacemaker was inserted, and subsequent transthoracic and transoesophageal echocardiograms showed severe aortic valve regurgitation with thickened cusps and thus raised suspicion of infective aortic endocarditis with root abscess. The patient underwent surgery with valve and root replacement the next day. What was thought to be IE, proved to be suppurative and granulomatous inflammation with sporadic necrosis and hyaline fibrosis, compatible with a rheumatoid nodule linked to the patient's RA diagnosis. Discussion: IE is a disease with high mortality and morbidity. In some cases of IE perivalvular cavities develop, most commonly abscesses and/or pseudoaneurysms, which necessitates surgery. Several conditions may mimic IE: for example, malignant and benign tumours, rheumatic diseases, and common age-related valve calcification. In patients with valvular vegetations that are 'culture-negative', alternative pathologies should be considered.