Macrophage Activation Syndrome - An Unusual Complication Of SLE

Macrophage Activation Syndrome (MAS) is a rare and potentially fatal condition that can complicate many autoimmune diseases. It is a type of Hemophagocytic Lymphohistiocytosis (HLH). HLH is a potentially fatal disease of normal but overactive histiocytes and lymphocytes commonly occurring in infancy but can occur in all age groups. There are two types of HLH: Familial and acquired. Familial HLH is an autosomal recessive disorder and accounts for 25% of the cases. Acquired type is secondary to drugs, malignancies, rheumatological disorders. There are five subtypes of inherited HLH: familial HLH and types 1-5. HLH may result from an inappropriate immune response to a viral illness like EBV. It may be due to X-linked Lymphoproliferative Disease (XLP) caused by a mutation in SH2D1A or XIAP gene. Usually, MAS term is used for HLH secondary to rheumatological disorders that occur mostly in individuals with Systemic Juvenile Idiopathic Arthritis (SJIA) and those with adult-onset Still disease. The condition is thought to be caused due to excessive activation and expansion of T lymphocytes and macrophage histiocytes that show hemophagocytic activity. The expansion of these cells leads to a massive systemic inflammatory response associated with three cardinal features: cytopenias, liver dysfunction, and coagulopathy, resembling Disseminated Intravascular Coagulation (DIC). MAS incidence in SLE patients is estimated to be 0.9% - 4.6%, and it is widely under recognized and underreported. In this report, we enumerate one such case with their clinical presentation, evaluation, and management.