[Serum type III procollagen N-terminal peptide in patients with collagen diseases].

The serum concentration of type III procollagen N-terminal peptide (P III P) level is known to reflect the activity of collagen biosynthesis. To analyze the correlation between the disease activity and serum P III P levels in collagen diseases, serum P III P levels in patients with rheumatoid arthritis (RA), progressive systemic sclerosis (PSS), and other collagen diseases were measured. In some patients serum levels of prolyl++-hydroxylase, which is an intra-cellular enzyme of collagen biosynthesis, were measured. Serum P III P levels were elevated in patients with PSS and MCTD/overlap syndrome, suggesting a high rate of collagen biosynthesis by fibroblasts. Patients with RA showed no significant elevation of serum P III P compared with normal control group. But the group of RA patients with elevated ESR and/or serum CRP values showed high levels of serum P III P. The correlation between the disease activity and serum P III P levels was observed in RA patients with positive rheumatoid factor (RF), but not patients without RF. In addition we measured P III P levels in synovial fluid of RA and osteoarthritis patients. The levels were one to three hundred times higher than serum levels, and they showed the positive correlation with serum levels, suggesting that serum P III P might be originated from synovial P III P.