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 th eir 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 cri teria, and 31 healthy controls were examined. Serum concentrations of amino terminal type III procollagen peptide (PIIINP), aminoterminal and carboxyte rminal type I procollagen peptides (PINP and PICP) and cross-linked carboxy terminal telopeptide of collagen I (ICTP) were determined by radioimmunoass ay. Results. Increased serum concentrations of ICTP were found in SSc patients compared with controls. Distinctly higher levels of ICTP were observed in d cSSc than in lcSSc. High serum ICTP was correlated with skin score and acut e phase reactants, and with reduced pulmonary function. Serum PIIINP concen tration was elevated in both lcSSc and dcSSc. Conclusion. Augmented collagen catabolism accompanies the increased collage n synthesis in SSc. Serum ICTP concentration is a marker of this feature an d also reflects clinical severity.