Interstitial hemophagocytosis in hemophagocytic lymphohistiocytosis

A 36-year-old woman with systemic lupus erythematosus and Sjögren syndrome—managed with prednisone (20 mg t.i.d.) and hydroxychloroquine (200 mg b.i.d.)—was admitted with fevers and pancytopenia. Pertinent laboratory values from initially performed testing can be found in Supplementary Table S1. A bone marrow biopsy showed evidence of hemophagocytosis. Infectious disease workup revealed the patient had latent tuberculosis. Examination was notable for fever (38.8 °C), a rash on the back, but no edema. Ultrasound and computed tomography showed evidence of splenomegaly, no lymphadenopathy or hepatomegaly, unremarkable brain findings, and normal kidneys. With fever, splenomegaly, cytopenias, and hemophagocytosis in the bone marrow, as well as elevated ferritin (1746 ng/ml) and serum interleukin 2 receptor (1791 pg/ml), the patient was diagnosed with hemophagocytic lymphohistiocytosis associated with rheumatologic/autoimmune and/or infectious processes. A kidney biopsy was performed secondary to proteinuria and hematuria (Figure 1; Supplementary Figure S1), revealing class II lupus nephritis and unexpectedly interstitial hemophagocytosis. Details of the patient’s subsequent clinical course and management are in Supplementary Table S2.