The authors report the case of a sixty-five year old woman initially suffering from a thrombocytopenia. The patient was diagnosed as having an autoimmune disease with a lupus anticoagulant, positive antinuclear antibodies and negative anti-DNA antibodies. She then developed an encephalopathy which was fatal despite corticosteroids. Brain pathology revealed a vasculitis with some giant cells, evoking a granulomatous angiitis of the central nervous system. These clinical and biological features suggest a systemic lupus erythematosus with vasculitis or a primary granulomatous angiitis of the central nervous system. Taking into account the clinical manifestations and the presence of a lupus anticoagulant, we finally preferred to identify it as a primary antiphospholipid antibodies syndrome, despite absence of anticardiolipin antibodies. Contrary to thrombosis, vasculitis is rarely associated with an anticardiolipin antibody or a lupus anticoagulant. However, vasculitis in the course of primary antiphospholipid antibodies syndrome has been reported previously as in this case report.