Hemophagocytic Lymphohistiocytosis (HLH) is a rare disorder that is characterized by overactive natural-killer and cytotoxic T cells that improperly trigger macrophages and subsequently leads to hemophagocytosis in bone marrow, spleen, liver, and lymph nodes. HLH can be found in primary (familial) or in secondary (acquired) forms. Diagnosis is made by Henter’s criteria. Bone marrow biopsy can be used for confirmation of diagnosis, if needed, and demonstrates elevated cellular activity and hemophagocytosis. Treatment for HLH consists of a chemo-immunotherapy regimen of etoposide, dexamethasone, and cyclosporine. Treatment is followed by transplant for patients with familial HLH or patients with secondary HLH who have severe or reactivated disease. To date, osteonecrosis in the setting of HLH is limited to individual case reports [1, 2].

Between 2005 and 2015, a total of 30 patients met the HLH diagnosis criteria, but 8 patients were excluded due to lack of cross-sectional imaging. Of the 22 patients with cross-sectional imaging, 10 patients were female and 12 patients were male. Five patients were diagnosed with familial HLH, while the remaining 17 patients fit the category of secondary HLH. The average age of diagnosis of HLH was 20.8 years, range 2 weeks–74 years. HLH-2004 therapy was started on 18 patients, and all remaining patients received high-dose steroids. A