COLLAGEN-DERIVED MARKERS OF BONE METABOLISM IN OSTEOGENESIS IMPERFECTA

Markers of bone formation [C-terminal and N-terminal propeptides of pr ocollagen I (PICP, PINP), osteocalcin and alkaline phosphatase] and bo ne resorption [C-terminal cross-linked telopeptide of collagen I (ICTP ) and hydroxypyridinium cross-links, pyridinoline (Pyr) and deoxypyrid inoline (Dpyr)] were measured in 78 osteogenesis imperfecta (OI) patie nts to investigate bone metabolism in vivo and relate marker concentra tions to phenotype and in vitro collagen I defects, as shown by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). PICP and PINP were generally low, and the serum levels were lower in all ch ildren and adults with mild OI and a quantitative collagen defect than in patients with severe OI and a qualitative collagen I defect. ICTP, Pyr and Dpyr were generally normal or reduced, but elevated in severe ly affected adults with a qualitative collagen I defect. The in vivo f indings correlated with in vitro results of collagen I SDS-PAGE. Bone turnover is reduced in OI children and mildly affected OI adults, wher eas bone resorption is elevated in severely affected adults. These fin dings may prove helpful for diagnosis and decision-making regarding th erapy in OI.