Prompt Recognition of Hemophagocytic Lymphohistiocytosis in an Afebrile Patient with Lupus and Staphylococcus aureus Bacteremia.

BACKGROUND Hemophagocytic lymphohistiocytosis (HLH) is a rare clinical syndrome characterized by dysregulated immune system activation and hyperinflammation. Primary HLH is inherited and almost exclusively seen in childhood, while secondary HLH is mainly seen in adults and has a wide variety of triggering factors, including infection, malignancy, autoimmune disease, and immunosuppression. Due to nonspecific presentation, the differential diagnosis for HLH is equally wide. We present a case of secondary HLH involving undiagnosed systemic lupus erythematosus and bacteremia. CASE REPORT A 43-year-old man with a history of discoid lupus presented with 1 month of weakness, epistaxis, shortness of breath, anorexia, and weight loss. He took no medications and did not follow with a primary care physician. Workup revealed leukopenia and thrombocytopenia, severely elevated ferritin, severe acute kidney injury, class II lupus nephritis on renal biopsy, hemophagocytic histiocytes on bone marrow biopsy, and other findings of end-organ damage. Blood cultures grew methicillin-sensitive Staphylococcus aureus (MSSA). Diagnosis of HLH occurred on the third day of admission. Our patient improved rapidly on high-dose corticosteroids, hydroxychloroquine, anakinra, tocilizumab, and low-dose etoposide as well as concomitant antibiotic therapy. CONCLUSIONS Despite having a diagnosis of discoid lupus, our patient was not established with a primary care physician and did not take any medications. This resulted in unknown smoldering systemic lupus erythematosus, which, possibly in conjunction with bacteremia, triggered a nearly fatal disease. We discuss the importance of primary care in disease management, the differentiation of sHLH from other diagnoses, HLH treatment, and the laboratory evaluation of sHLH.