Unexpected macrophage activation syndrome in a healthy young woman: a case report.

Macrophage activation syndrome (MAS) is a life-threatening condition and a medical emergency with a high-risk of mortality. It belongs to a group of diseases known as "hemophagocytic lymphohistiocytosis", characterized by a cytokine storm, with secretion of tumor necrosis factor, interleukins and interferon-gamma, and an inappropriate activation of macrophages and T-lymphocytes. Some inflammatory and systemic autoimmune diseases, such as systemic juvenile idiopathic arthritis, Still's disease and systemic lupus erythematosus, can develop into macrophage activation syndrome. This is the first episode of macrophage activation syndrome (MAS) in a young healthy woman. She arrived at the Emergency Department complaining of four days of weakness and fever not responsive to paracetamol. She had no significant past medical history, her mother suffered from rheumatoid arthritis. In the Emergency Department, we performed laboratory exams, autoimmune and infectious disease screening, bone marrow biopsy. The final diagnosis was of macrophage activation syndrome. Macrophage activation syndrome, in extremely rare cases, can arise independently years before the manifestation of an autoimmune disease. Persistent fever, high level of inflammatory markers and pancytopenia should raise suspicion in healthy people, especially when associated with a family history of autoimmune disease. Early diagnosis and consequent early treatment are fundamental to avoid progressive tissue damage that can lead to organ failure and death.