Correlation of serum collagen I carboxyterminal telopeptide concentrations with cutaneous and pulmonary involvement in systemic sclerosis.

Abstract

Systemic sclerosis (SSc) is characterized by fibrosis involving the skin and various internal organs. Type I collagen (Col I) is the most abundant extracellular matrix protein deposited in cutaneous involvement. We investigated Col I biochemical markers in patients with SSc. All consecutive patients admitted for SSc over a 9 month period and a healthy control group were investigated. Serum concentrations of the C-terminal telopeptide of Col I (s-CTX-I), C-terminal type I procollagen propeptide (PICP), osteocalcin, and bone alkaline phosphatases (ALP), and urinary concentrations of deoxypyridinoline (u-DPD) and u-CTX-I were determined by ELISA. A total of 33 patients with SSc were included: mean age +/- SD was 54 +/- 12 yrs, with a mean disease duration of 5.4 +/- 3.9 years. Sixteen of 33 patients with SSc had s-CTX-I values exceeding the upper limit of normal values of the test and the mean +/- SEM was significantly higher (7388 +/- 1422 pmol/l) than in healthy controls (2800 +/- 1120 pmol/l; p < 0.001). s-CTX-I correlated with the Rodnan skin score (p = 0.003); it was higher in patients with diffuse disease (8459 +/- 3125; n = 14) than in patients with the limited form (6453 +/- 1235; n = 19; p < 0.02). This marker also correlated with acute phase reactants (C-reactive protein, p = 0.004; erythrocyte sedimentation rate, p = 0.02). s-CTX-I was high in patients with positive antitopoisomerase I autoantibodies (p = 0.04) and in patients with a decrease in forced vital capacity to less than 75% (p = 0.02). u-DPD concentration was high in patients with SSc (10.6 +/- 1.4 nmol/mmol creatinine vs 6.3 +/- 2.1 in controls; p < 0.01). No difference between patients and controls or correlations with the disease were found for PICP, u-CTX-I, osteocalcin, and bone ALP concentrations. s-CTX-I, a marker of Col I degradation, is correlated with cutaneous and pulmonary involvement and with acute phase reactants in patients with SSc. This marker is a good candidate for further evaluation for disease activity and treatment purposes.