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Initial diagnosis of Macrophage Activation Syndrome

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Medical Paediatrics


Macrophage activation syndrome (MAS) is a rare hyperinflammatory condition, one of the increasingly-recognised cytokine storms, seen in children and adults with underlying rheumatological disorders. MAS requires prompt recognition and aggressive treatment as untreated the mortality rate is 8-22%.

This guideline focusses on MAS in the context of rheumatological disorders. If the child does not have a known underlying diagnosis, the differential diagnoses of primary or secondary HLH and MAS as part of the initial presentation of a rheumatological disorder should be considered.


  • Definition
  • Urgent Investigations
  • Published Diagnostic & Classification Criteria
  • Initial Treatment
  • Additional Considerations
Editorial Information

Last reviewed: 01 March 2022

Next review: 31 March 2025

Author(s): Scottish Paediatric & Adolescent Rheumatology Network

Version: 2

Approved By: Scottish Paediatric & Adolescent Rheumatology Network

Document Id: NSD610-013.05