About MAS
MAS: A hyperinflammatory syndrome with devastating effects in rheumatic diseases1-3
Macrophage activation syndrome (MAS) is a subtype of hemophagocytic lymphohistiocytosis (HLH). HLH can be associated with a variety of underlying conditions, including infection, malignancy, and rheumatic disease. MAS is the term used for HLH that is associated with underlying rheumatic diseases.1
MAS is characterized by:
Interferon gamma (IFNγ)-hyperactivated macrophages that release an uncontrolled surge of proinflammatory cytokines.4
Systemic hyperinflammation that can become life-threatening.2
MAS as a complication of Still’s disease
MAS frequently occurs in patients with Still's disease, including both systemic juvenile idiopathic arthritis (sJIA) and adult-onset Still's disease (AOSD). For patients with known Still’s disease, the manifestations of MAS may often be confused with a flare of their underlying disease. MAS may also occur at the onset of Still’s disease, so it is critical to maintain suspicion in patients who have not been previously diagnosed with an underlying rheumatic disease.1
The clinical presentation of MAS can overlap with2,3,5-8:
- Malignancy
- Liver failure
- Infection
- Immune disorders
- Anemia
- Kawasaki disease
- Flares of rheumatic disease, including AOSD, sJIA, and lupus
MAS signs and symptoms
In patients with MAS, uncontrolled levels of proinflammatory cytokines overwhelm multiple organ systems. This may initially present as general malaise in early stages but can quickly progress to widespread damage.1,9,10 More specific signs and symptoms include5,6,10,*:
- Persistent fever
- Hyperferritinemia
- Hypertriglyceridemia
- Liver dysfunction
- Lymphadenopathy
- Coagulopathies, including cytopenias and coagulation defects (easy bruising or bleeding, petechial or purpuric rash)
- Central nervous system (CNS) involvement
- Hemophagocytosis
Unresolved MAS may progress to multiple organ failure and is associated with mortality rates up to 39%.3
*This is not an exhaustive list of MAS signs and symptoms. Presentation may vary between patients, and it is not necessary to identify all of these symptoms to diagnose MAS.