Undiagnosed Systemic Lupus Erythematosus Presenting as Hemophagocytic Lymphohistiocytosis

Hemophagocytic Lymphohistiocytosis (HLH) is rarely diagnosed in adults. Incidence is reported as one case per million persons per year. It can be triggered by conditions that affect immune homeostasis as infections, malignancies, and rheumatologic disorders. The following case demonstrates a rare instance in which undiagnosed systemic lupus erythematosus (SLE) presented as HLH. A 28-year-old male presented with progressive weakness and recurrent fevers for 2 months. Vital signs were within normal limits except for temperature of 100.3°F. His exam was unremarkable except for a left cervical scar and malar rash. His labs showed pancytopenia with neutropenia, hypertriglyceridemia, hypofibrinogenemia, and hyperferritinemia. Hemophagocytosis was present on bone marrow biopsy. All workup for a source of infection was negative. A tentative diagnosis of HLH was made based on clinical presentation and laboratory data. The patient was treated with an HLH protocol. Later, it was determined that his HLH was actually secondary to a primary diagnosis of SLE. The patient was treated for SLE with an immunosuppressive regimen of cyclosporine and dexamethasone, and he improved dramatically. HLH rarely presents due to a rheumatologic condition such as SLE. Physicians should consider testing for SLE in patients diagnosed with HLH.