Elevated serum levels of neopterin in adult patients with polymyositis/dermatomyositis

We determined serum concentrations of neopterin, soluble tumour necrosisfactor (55 kDa) receptor (sTNF-R) and soluble interleukin-2 receptor(sIL-2R) in plasma of 44 patients with polymyositis (PM)/dermatomyositis(DM), including 15 patients with primary PM, 13 patients with primary DM,and 16 patients with myositis and systemic sclerosis in overlap.Concentrations of neopterin, sTNF-R and sIL-2R were measured usingcommercially available immunoassays. Serum neopterin was increased in 35 of44 PM/DM patients (80%), sTNF-R in 14 (32%) and sIL-2R in 18 (41%)patients, respectively. There were significant correlations between serumneopterin and sTNF-R, sIL-2R and erythrocyte sedimentation rate (all P <0.001). Neopterin, as well as sTNF-R and sIL-2R, did not correlate withclinical (neuromuscular and activities of daily living scores) andlaboratory (creatine kinase levels) manifestations of myositis. Increasedserum levels of neopterin were associated with non-muscular manifestationsof PM/DM. In conclusion, serum neopterin appears to be a useful laboratorymarker for ongoing immune activation and global disease activity in PM/DM.