Effect of Treatment with Bisphosphonates on Bone Turnover Markers in Osteogenesis Imperfecta

Abstract Background Bisphosphonates are used as standard treatment in patients with osteogenesis imperfecta (OI) in childhood and adolescence. N-terminal collagen type I extension propeptide (PINP) has been identified as the most promising marker of bone formation. Aim and Objectives Our study aimed to use PINP as a marker of bone formation in patients with OI receiving bisphosphonates treatment. Patients and Methods This observational study included 28 with OI patients (12 boys & 16 girls) on bisphosphonates treatment following up at Pediatric Endocrinology Clinic, Ain Shams University Children's Hospital during the period from March 2021 till April 2022. PINP was measured at baseline and one year after treatment. Clinical severity score was evaluated. Results (53.6%) of patients were classified as moderate degree of clinical severity score. Clinical severity score domains were as follows: (67.9%) of patients were classified as grade I regarding number of fractures per year (0-1), (50.0%) of patients were classified as grade II regarding motor milestones (delayed with catch up), (46.4%) of patients were classified as grade III regarding long bone deformities (noticed by both clinical examination and X-rays affecting isolated long bones) and regarding height SDS (-3.1 to -5.0), while (46.4%) of patients were classified as grade I regarding DXA Z-score (< -1.5 SD). PINP decreased <20% in 6 patients (21.4%) and increased <20% in 5 patients (17.9%). There was no change in 17 patients (60.7%). Furthermore, there was no significant relation between PINP and clinical severity score. Conclusion PINP change in patients with OI on bisphosphonates treatment might not be pronounced or sustained after treatment, thus might not reflect the clinical status of the patients on short term basis.