A Diagnostic Dilemma: Adult-Onset Still's Disease With Secondary Hemophagocytic Lymphohistiocytosis/Macrophage Activation Syndrome?

Adult-onset Still's disease (AOSD) is a rare autoinflammatory condition. It is a diagnosis of exclusion by ruling out all related infectious, inflammatory, autoimmune, and malignant diseases. We present a case of a 23-year-old Caucasian male who presented with fever, night sweats, joint pain, weight loss, and diarrhea. The initial presentation delayed the diagnosis. Upon further investigation, we formulated the diagnosis of AOSD. In sporadic cases, AOSD with secondary hemophagocytic lymphohistiocytosis (HLH), also known as macrophage activation syndrome (MAS), is a devastating disorder of uncontrolled immune activation characterized by clinical and laboratory evidence of extreme inflammation. In case of suspected secondary complications, timely involvement of a multidisciplinary team and starting of appropriate medications is necessary.