Circulating collagen metabolites in systemic sclerosis. Differences between limited and diffuse form and relationship with pulmonary involvement.

OBJECTIVE To study collagen metabolites in systemic sclerosis (SSc) and their relationship with clinical manifestations of the disease. METHODS Forty-eight SSc patients, 13 with a diffuse form (dcSSc), 23 with a limited form (lcSSc) and 12 with suspected SSc not fulfilling the ACR criteria, and 31 healthy controls were examined. Serum concentrations of aminoterminal type III procollagen peptide (PIIINP), aminoterminal and carboxyterminal type I procollagen peptides (PINP and PICP) and cross-linked carboxyterminal telopeptide of collagen I (ICTP) were determined by radioimmunoassay. RESULTS Increased serum concentrations of ICTP were found in SSc patients compared with controls. Distinctly higher levels of ICTP were observed in dcSSc than in lcSSc. High serum ICTP was correlated with skin score and acute phase reactants, and with reduced pulmonary function. Serum PIIINP concentration was elevated in both lcSSc and dcSSc. CONCLUSION Augmented collagen catabolism accompanies the increased collagen synthesis in SSc. Serum ICTP concentration is a marker of this feature and also reflects clinical severity.