Hemophagocytic Lymphohistiocytosis Secondary to Adult-Onset Still's Disease.

Hemophagocytic lymphohistiocytosis (HLH) is a rare hematological condition resulting from dysregulation of the immune system. This unusual clinical syndrome is characterized by fever, cytopenia, liver dysfunction, increased ferritin level, and evidence of hemophagocytosis in the bone marrow. We report a case of a 21-year-old female who presented with recurrent high-grade fever, transient rash, and polyarthritis who was subsequently diagnosed with adult-onset Still's disease (AOSD) with secondary HLH. The patient improved with aggressive management. Our case highlights HLH as a life-threatening and underdiagnosed complication of AOSD.