Increased urinary pyridinoline cross-link compounds of collagen in patients with systemic sclerosis and Raynaud's phenomenon

Objective. To study concentration changes in collagen degradation markers inpatients with diffuse and limited cutaneous systemic sclerosis and patients with scleroderma-related diseases. Methods. Pyridinoline cross-link compounds were analysed in urine samples using high-performance liquid chromatography. Samples were analysed for pyridinoline (Pyr), deoxypyridinoline (Dpyr) and soft-tissue pyridinoline (stPyr) in patients with diffuse cutaneous systemic sclerosis (dcSSc, n = 23) and limited cutaneous systemic sclerosis (IcSSc, n = 48) and in patients with scleroderma-related diseases such as primary Raynaud's phenomenon (pRP, n = 16) and secondary Raynaud's phenomenon (sRP, n = 14). Healthy controls (n = 18) and patients with post-menopausal osteoporosis (OP, n = 35) were also investigated. Results. Urinary Pyr, Dpyr and stPyr concentrations were significantly higher in patients with Raynaud's phenomenon and systemic sclerosis than in healthy controls. The highest concentrations (two to three times greater than in healthy controls) were found in patients with dcSSc. The stPyr concentration was significantly higher in patients with dcSSc than in those with IcSSc, sRP and pRP. No significant difference in stPyr concentration was found between the healthy controls and the OP group, suggesting that stPyr is derived from soft tissues rather than bone. The extent and severity of skin involvement, measured as a skin score, significantly correlated with the concentrations of stPyr and Pyr, whereas no such correlation was found for Dpyr. Conclusions. Increased urinary concentrations of piridinoline cross-links reflect alterations in collagen turnover in both Raynaud's phenomenon and systemic sclerosis. The close correlation between stPyr concentration and the extent of skin involvement in systemic sclerosis suggests that this parameter may be useful in monitoring ongoing fibrosis in this disease.