Serum ferritin is an acute phase reactant, which can be elevated due to any acute infection, rheumatological illness or infiltrative disease.
Elevated serum ferritin is seen in rheumatological illnesses such as Systemic onset juvenile idiopathic arthritis(SOJIA) and Macrophage activation syndrome(MAS). MAS can be secondary to infections, malignancies or autoimmune diseases such as SOJIA, systemic lupus erythematosus and Kawasaki disease. In SOJIA, ferritin levels correlate well with disease activity. A marked increase in ferritin is an important indicator for MAS especially when it is >10,000 ng/ml.
Lately, it again gained interests in Pediatric practice as incidence of Post Covid illness (MIS-C) increased post Covid-19 wave, but its interpretation needs a critical analysis after having ruled out other etiologies, especially when Covid Seropostivity rates are increasing in pediatric population.