Introduction Hemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory syndrome that is associated with a high mortality rate. HLH is characterized by hemophagocytosis and histiocytic proliferation (1). Primary HLH has a familial pattern and secondary HLH is reactive and also called macrophage activation syndrome (MAS). This type of HLH is usually acquired following autoimmune diseases, infection, and malignancy (2).The prevalence of HLH is not completely measurable because the diagnosis of this disease is hard and there are other comorbid diseases at the time of diagnosis. In a study that was done in Sweden from 1987 to 2006, the prevalence of HLH was 1.5 per million (3).The manifestations of HLH are fever and cytopenia. The diagnosis of HLH is made by clinical suspicion of physicians. The criteria for diagnosis of HLH include fever; splenomegaly; cytopenia (affecting at least two of three lineages in the peripheral blood); fasting triglyceride levels ≥3 mmol/L and/or fibrinogen level ≤1.5 g/L; serum ferritin level ≥500 ng/ml; CD25 level ≥2400 U/ml; decreased or absent natural killer (NK) cell activity; or hemophagocytosis in bone marrow, spleen, or lymph nodes (4).Adult-onset Still’s disease (AOSD) is an autoimmune disorder that can predispose patients to HLH. The co-incidence of AOSD and HLH is rare (5).In this report, we present a woman with a co-incidence of AOSD and HLH.