Reactive hemophagocytic syndrome (HS) occurs mainly in the setting of serious infections and lymphomas. HS can occur in the course of 2 active systemic diseases, without simultaneous infection: adult Still disease and systemic lupus erythematosus (SLE). Observations of specific lupus-associated HS are rare, and the long-term outcome of these patients with active SLE is unknown. We retrospectively studied 15 episodes of SLE-associated HS in 12 patients (10 women, 2 men) and noted the long-term outcome. HS occurred at a mean age of 25 years. All patients were febrile with >or=2 cytopenias, and bone marrow aspiration indicated hemophagocytosis. HS revealed SLE in 9 patients and recurred in 3. The main features of SLE-associated HS were a low frequency of hepatosplenomegaly, a high frequency of heart involvement (5 pericarditis, 4 myocarditis requiring transfer to intensive care unit), and a low C-reactive protein level (mean, 15 mg/L). Cutaneous-mucous symptoms of SLE, arthritis, and nephritis were present respectively in 8 (53%), 6 (40%), and 4 (27%) episodes, but symptoms of SLE were absent in 4 episodes at admission. All patients had anti-nuclear antibodies when the HS occurred. Anti-double-stranded DNA antibodies were present in 12 episodes. Treatment was steroids in 14 cases but cyclophosphamide was the only treatment able to control HS in 2 cases. All the cases of SLE-associated HS were controlled by the immunosuppressive regimen. Intravenous immunoglobulins seemed poorly effective. No infectious agent was found. Clinical presentations of the 23 patients with SLE-associated HS described in the literature were reviewed and were similar to those of the current series. The mean follow-up was 88 months (range, 7-240 mo). One patient died at 15 months (sepsis). Among the 5 patients with a follow-up >8 years, 4 always had active disease. During the follow-up of SLE, immunosuppressive drugs were added in 8 patients (cyclophosphamide in 7, azathioprine in 3, mycophenolate mofetil in 2) with significant adverse drug reactions. In the long-term, SLE-associated HS seems to define a severe SLE form with frequent flares, possible HS recurrences, and the need for prolonged immunosuppression.