Soluble CD25 in serum: a potential marker for subclinical macrophage activation syndrome in patients with active systemic onset juvenile idiopathic arthritis.

OBJECTIVE

Laboratory and immunological abnormalities seen in overt macrophage activation syndrome (MAS) may be observed in patients with untreated new onset systemic onset juvenile idiopathic arthritis (SoJIA). We investigated the prevalence of clinical and traditional laboratory markers of MAS as well as soluble CD163 and soluble interleukin (IL)-2Rα (CD25) in active SoJIA patients.

METHODS

Thirty-three consecutive patients with active SoJIA (International League of Associations for Rheumatology criteria), 11 patients with active polyarticular JIA (polyJIA) (disease control) and two patients with MAS with SoJIA were included in the study. Clinical data, complete blood count, coagulation profile, biochemical tests were performed. Soluble CD25 and soluble CD163 levels were estimated by enzyme-linked immunosorbent assay.

RESULTS

Of the 33 active SoJIA patients, 22 were male, the mean age at onset of disease was 6.77 ± 4.48 years and the duration of disease was 4.39 ± 4.6 years. Of the 11 polyJIA patients seven were boys. None of the SoJIA patient had clinical features of MAS. Fibrinogen < 2.5 g/L was present in 14/33 patients with SoJIA but in only 1/11 in polyJIA. Both patients with MAS had thrombocytopenia, leucopenia and reduced fibrinogen levels. sCD25 > 7500 pg/mL seen in MAS was present in eight patients with active SoJIA. Among these eight patients, four had multiple laboratory abnormalities suggestive of MAS. Indeed, one of the patients had past history of MAS. Elevated sCD63 (> 1800 ng/mL) was seen in four patients with SoJIA.

CONCLUSION

Laboratory abnormalities associated with MAS are not uncommon in active SoJIA. Soluble CD25 > 7500 pg/mL may be a marker to detect children with subclinical MAS.