Serum concentrations of carboxyterminal propeptide of type 1 procollagen and tissue inhibitor of metalloproteinase 1 in patients with dermatomyositis

Abstract Serum levels of carboxyterminal propeptide of type I procollagen (PICP) and aminoterminal propeptide of type I procollagen (PINP) have been used as indices of collagen synthesis in patients with various fibrotic diseases during the active stages. One of the suggested contributory factors to the development of tissue fibrosis is a decrease in collagenase activity, which may be related to levels of serum tissue inhibitors of metalloproteinases-1 (TIMP-1). In this study, the serum levels of PICP and PINP in 20 patients with dermatomyositis and 29 control subjects and of TIMP-1 in 29 patients with dermatomyositis and 29 control subjects were measured using an enzyme-linked immunosorbent assay (ELISA) or a radioimmunoassay (RIA). We found that the mean PICP level in patients with dermatomyositis was significantly higher than that in normal controls (mean ± SD 326 ± 76 ng/ml vs 135 ± 88 ng/ml; P < 0.001). In 60% of dermatomyositis patients, the serum PICP level was elevated (more than 311 ng/ml, i.e. 2 × SD above the mean control value). Elevated serum PICP levels were correlated with the incidence of elevated serum creatine kinase levels in patients with dermatomyositis. The serum concentration of PINP was not elevated in comparison with that of the normal control subjects (mean ± SD 36 ± 30 ng/ml vs 63 ± 34 ng/ ml). The mean TIMP-1 level in the patients with dermatomyositis was also significantly higher than in the normal control subjects (mean ± SD 438 ± 328 ng/ml vs 163 ± 63 ng/ml; P < 0.001). In 59% of dermatomyositis patients, the mean serum TIMP-1 level was elevated (more than 289 ng/ml, i.e. 2 × SD above the mean control value). Serum PICP and TIMP-1 levels might be useful for detecting disease activity or severity in dermatomyositis.