Background: Mechanisms underlying arterial thrombosis in younger patients are still unknown. Case: A 35-year-old man free of cardiovascular risk factors was admitted to hospital for severe ischemia in lower limbs due to thrombosis, and urgent embolectomy was done. Transoesophageal echocardiography and MRI showed pedunculated structure of 2.6x13cm attached to aortic arch wall. Patient required anticoagulant therapy. Thrombophilia screening yielded negative results. His mother had aortic arch thrombosis at the age of 42. Plasma fibrin clot testing revealed abnormal features of plasma fibrin clot structure/function. We conclude, unfavorably altered fibrin characteristics might predispose to arterial thrombosis at untypical locations.