Hemorrhagic events due to production of antibodies directed against coagulation factors are rarely observed in systemic lupus erythematosus (SLE). We report the case of a patient with clinically quiescent SLE who developed factor VIII inhibitor in acquired hemophilia presenting as hemarthrosis. Initial treatment with FVII, FVIII and FIX plasma concentrate, metilprednisolone and immunoglobulins i.v. were started but new hemorrhagic manifestation occurred. Plasma exchange was also administered, but it was discontinued early due to partial efficacy. In addition, pulse cyclophosphamide 0.5 g/m(2) was started. Eight weeks later, FVIII and FIX activity returned within normal ranges, FVIII and FIX inhibitors decreased significantly and hemorrhagic manifestations disappeared. The rare occurrence of acquired hemophilia due to the presence of anti-factor VIII antibodies associated to SLE, which was reviewed, might explain the lack of therapeutic guide-lines; indeed therapeutic options are available but the outcome in each single patient is not predictable.