[Various indices of collagen metabolism in children with rheumatoid arthritis].

To study collagen metabolism, 113 children aged 3 to 14 years afflicted with rheumatoid arthritis and 43 conventionally normal children were examined. The patients were examined for free and protein-bound hydroxyproline in the blood serum and synovial fluid and for total hydroxyproline in diurnal urine. The blood serum and synovial fluid showed a decline of free and a rise of protein-bound hydroxyproline, more marked in severe rheumatoid arthritis, its higher activity and damage to numerous joints. Excretion of free and total hydroxyproline with urine was significantly lower than in the normal children whatever the form of rheumatoid arthritis, its activity or number of the joints involved into the process. In view of the lack of hydroxyprolinuria in the sick children, the authors discuss a hypothesis of a potential initial decrease of collagen formation in children afflicted with rheumatoid arthritis, suggesting its relationship to the "ligand pathology".