Off-Label Use of Teriparatide for Osteotomy Healing in an Adolescent with Osteogenesis Imperfecta Type VIII: A Case Report.

Osteogenesis imperfecta (OI) type VIII is an autosomal recessive skeletal dysplasia caused by P3H1 variants, resulting in defective collagen post-translational modification and increased bone fragility. Teriparatide (TPTD), a recombinant parathyroid hormone analogue, stimulates osteoblast activity and bone formation and is approved for the treatment of osteoporosis in adults. A 16-year-old male with genetically confirmed OI type VIII presented with delayed union with characterized by the absence of radiographic evidence of healing six months after femoral osteotomy and intramedullary rodding surgery. His prior management included intermittent bisphosphonate therapy which had improved bone mineral density. He had no recent history of fractures. Off-label therapy with TPTD (20 µg/day subcutaneously) was initiated and continued for six months. Although systemic markers of bone formation showed no remarkable changes, except osteocalcin, during therapy, serial radiographs confirmed successful bone union. The treatment was well tolerated, with no reported side effects; however, mild hypercalcemia with hypercalciuria, which persisted after discontinuation of TPTD therapy, was detected. Bisphosphonate therapy was resumed upon completion of TPTD treatment. This case represents the first documented use of TPTD to promote osteotomy healing in an adolescent with OI. The favourable clinical and radiologic outcome suggests a potential role for anabolic therapy in managing complex bone healing challenges in paediatric OI. Further research is warranted to evaluate safety and efficacy in this population.