Behçet's disease is a chronic autoimmune disease with vascular complications that are most frequently manifested as thromboembolism in veins and pseudoaneurysm in arteries. We report the case of a 13-year-old boy admitted for clinical and biological signs of rheumatic fever associated with chest pain. The clinical examination found heart sounds with a discrete systolic murmur of mitral regurgitation. The electrocardiogram showed a microvoltage with diffuse repolarisation disorder. Biologically, he had inflammatory syndrome. Transthoracic echocardiography showed circumferential pericardial effusion with anterosepto-apical hypokinesia of the left ventricle with systolic dysfunction, and a minimal mitral regurgitation. The patient was treated by corticotherapy and antibiotherapy. The outcome was marked by orogenital aphthous ulceration and decreased visual acuity related to intermediate uveitis. The retinal angiography showed a vasculitis. The late appearance of this symptom led to the right diagnosis of Behçet's syndrome. Transthoracic echocardiography showed a hypokinetic dilated cardiomyopathy left ventricular with septo apical and anterior akinesia and severe systolic dysfunction, with a defect of the inferior septal with a collar communicating the left ventricle with a giant pseudo aneurysm. Magnetic resonance imaging showed a giant pseudoaneurysm communicating with the left ventricle. The coronary computed tomography was normal. The patient had undergone surgical treatment for the pseudoaneurysm with good outcomes.