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Objectives To report a case of secondary hemophagocytic lymphohistiocytosis (HLH) in a patient with systemic lupus erythematosus (SLE), highlighting its challenges and successful treatment with IL-1 blockade.Methods We report a case of SLE complicated by HLH. Diagnostic workup included blood counts, liver function tests, inflammatory markers, thoraco-abdomino-pelvic and cerebral imaging, cerebrospinal fluid (CSF) analysis, viral and bacterial screening. HScore was calculated to assess HLH probability (1).Results A 41-year-old woman with SLE since age 28, with previous cutaneous, articular e serosae involvement, on baseline therapy with hydroxychloroquine 200 mg/day and prednisolone 10 mg/day due to recent flare with pericarditis and pleural effusion, presented, in July 2025, odynophagia, severe headache, myalgia, high fever, general malaise and asthenia. She had no other accompanying symptoms, such as cutaneous lesions, cough, dyspnoea, chest pain or urinary symptoms.Initial laboratory findings revealed liver cytocholestasis, elevation of C-reactive protein (13.5 mg/dL), low erythrocyte sedimentation rate (17mm), and normal blood counts. Thoracic and abdominal computer tomography (CT) showed multiple adenopathies and mild hepatomegaly; cerebral CT did not show any brain lesions or thrombosis. CSF had mild protein elevation, without pleocytosis or glucose consumption. Blood cultures and CSF viral antigens search and cultures were negative. Viral serologies were negative for hepatitis B and C virus, human immunodeficiency virus, parvovirus B19 and Epstein-barr virus and positive for cytomegalovirus (CMV) IgG/IgM, though without detectable viral load.During hospitalization, she developed thrombocytopenia, progressive liver enzyme dysfunction, hyperferritinemia and hypertriglyceridemia. She also presented an acute confusional state. Brain MRI revealed nonspecific changes.Suspection of HLH arised and fibrinogen level was low, HScore was 194 points, supporting HLH diagnosis.Treatment with IL-1 antagonist anakinra for 10 days led to rapid clinical and laboratory improvement.Conclusions HLH is a rare and potentially life-threatening complication in SLE, often triggered by infections, and difficult to distinguish from lupus flare (2–4). Early recognition and prompt therapy, such as IL-1 blockade, can result in rapid recovery. This case underscores the importance of systematic evaluation of persistent fever, cytopenias, hyperferritinemia, and organ dysfunction in SLE patients and the need to actively investigate viral infections in this context.