Macrophage Activation Syndrome (MAS)

Classified among the secondary or acquired forms of haemophagocytic lymphohistiocytosis (sHLH)



What?

A subset of hemophagocytic lymphohistiocytosis (HLH) that develops on the background of a highly inflammatory disease



How?

Excessive release of pro-inflammatory cytokines, such as IL-1 and IL-6, leading to widespread inflammation via hemophagocytosis and cytokine overproduction.



Where?

Seen in:

• Systemic juvenile idiopathic arthritis (sJIA)

• Adult-onset Still disease

• Systemic lupus erythematosus

• Kawasaki disease

• Periodic fever syndromes



Clinical Presentation:

• Rapid development of multiorgan failure

• Fever is the main clinical manifestation of MAS - Nonremitting fever

• Hepatosplenomegaly and generalized lymphadenopathy

• Central nervous system (CNS) dysfunction

• Hemorrhagic manifestations: from easy bruising to purpura to mucosal bleeding (Petechial or purpuric rash)

• Heart, lung, and kidney failure



DDX:

• Flare of underlying disease (eg, systemic juvenile idiopathic arthritis [SJIA], systemic lupus erythematosus [SLE], AOSD)

• Infection (eg, visceral leishmaniasis, brucellosis)

• Sepsis

• Drug-induced hypersensitivity syndromes

• HLH



Labs:

• Profound cytopenia with leukopenia, anemia, and thrombocytopenia

• Liver function tests ↑ AST ↑ ALT ↑ bilirubin level

• Hypoalbuminemia

• Hypofibrinogenemia

• ↑ PT ↑ PTT

• ↑ Fibrin degradation products

• ↑ D-dimers

• ↑ Triglycerides

• ↑ Lactate dehydrogenase

• ↑ Ferritin > 5000 to 10,000 ng/mL

• Hyponatremia

• Increased soluble IL-2 receptor alpha (or soluble CD25)

• Increased soluble CD163

• Histopathologic features

• Macrophage hemophagocytosis in the bone marrow

• Increased CD163 staining of bone marrow



Histopathologic criteria:

Evidence of macrophage hemophagocytosis is found in the bone marrow aspirate sample.



Treatment:

• Corticosteroids

• IVIG

• Cyclophosphamide

• Plasma exchange



#MAS #Macrophage #Activation #Syndrome #Diagnosis #Management #Hematology #Rheumatology