Type I collagen as a marker of bone metabolism in sickle cell hemoglobinopathies

Avascular necrosis of the skeletal system is a complication of sickle cell hemoglobinopathies. Type I collagen, which is synthesized by osteoblasts, comprises about 90% of the total organic matrix of bone. This preliminary study of skeletal changes in sickle cell hemoglobinopathies measured type I collagen formation and degradation using specific radioimmunoassays to determine the plasma concentrations of carboxyterminal propeptide of type I procollagen (PICP) and carboxyterminal pyridinoline cross-linked telopeptide of type I collagen (ICTP), respectively. Plasma ICTP concentrations were increased significantly in sickle cell patients with no clinical or radiologic symptoms of bone complications than in controls. Mean plasma ICTP concentration was moderately high in all patients. Plasma PICP levels did not differ significantly between patients and controls. This preliminary results indicate that measurements of plasma ICTP might be helpful in predicting bone changes in sickle cell hemoglobinopathies and also useful in the early detection of skeletal complications of the disease.