Thromboangiitis obliterans is a segmental obliterating inflammatory arteritis, usually found in young (below 40) smoking males. Its diagnosis relies on patient history, clinical features, arterial angiography, and more rarely on pathological findings, though none of these is specific of the disease, and on the absence of other diseases such as early atheroma, thromboembolic processes, vascular malformation, trauma, collagen or blood disorders. Raynaud's phenomenon, digital arteritis, superficial and often migrating venous thromboses are further arguments for the disease. However, such associations can also occur during other diseases, especially congenital or acquired deficits in coagulation factors (antiphospholipid syndrome, S protein deficiency...). In our patient with suspected thromboangiitis obliterans, the occurrence of superior longitudinal and right lateral sinus thrombosis led to the discovery of a qualitative C protein defect. This observation stresses the need for careful elimination of a coagulation disorder before confirming the diagnosis of thromboangiitis obliterans.