C-reactive protein in juvenile chronic arthritis: an indicator of disease activity and possibly amyloidosis.

C-reactive protein (CRP) was found to be particularly high early in the course of those cases of juvenile chronic arthritis (JCA) with a systemic onset, the mean level being 12 mg/dl (120 mg/l). It was also raised in cases with a polyarticular onset, mean level 6 mg/dl, while in cases with a pauciarticular onset it was associated with only a modest increase up to 1.5 mg/dl (15 mg/l). At the onset of disease there was a good correlation with the erythrocyte sedimentation rate (ESR). Regression of systemic disease was associated with a steady fall in C-reactive protein, but those patients who developed amyloidosis within 5 years from onset had persistently high values until cytotoxic therapy was introduced. Patients who developed amyloidosis later tended to have high CRP levels in the months or even years before diagnosis. In a few patients with polyarthritis the CRP appeared to reflect severe disease more closely than their relatively low ESR.