Clinical Pearl at #ACR21 from Dr. J. Stone:
⭐️Ferritin:ESR ratio helps distinguishes systemic JIA flares from macrophage activation syndrome (MAS).

⭐️During MAS:
*️⃣Ferritin rapidly rises as an acute phase reactant
*️⃣ESR declines as fibrinogen is consumed.
#ACRBest @RheumNow