EBV-triggered secondary macrophage activation syndrome in the backdrop of lupus in an adult.

Macrophage activating syndrome (MAS) is a potentially life-threatening condition falling under the spectrum of secondary hemophagocytic lymphohistiocytosis, in the backdrop of rheumatological conditions. In this case of a middle-aged man, we see how an initial Epstein Barr virus infection triggered a chain of events, which after serial monitoring of labs was promptly diagnosed as MAS and treated appropriately, resulting in overall clinical improvement of the patient.