Study to Evaluate Romosozumab in Children and Adolescents with Osteogenesis Imperfecta

Inclusion Criteria: • Ambulatory male or female children 5 to less than 18 years of age upon entry into screening • Clinical diagnosis of OI defined as a clinical history consistent with type I-IV OI as determined by presence of expected phenotype and lack of additional features unrelated to type I-IV OI Exclusion Criteria • History of an electrophoresis pattern inconsistent with type I to type IV OI • History of known mutation in a gene other than collagen type I alpha 1/collagen type I alpha 2 (COL1AI/COL1A2) causing OI or other metabolic bone disease • History of other bone diseases that affect bone metabolism (eg, osteoporosis pseudoglioma syndrome, idiopathic juvenile osteoporosis, osteopetrosis, hypophosphatasia) • History of Kawasaki disease, rheumatic myocarditis, ischemic cardiomyopathy, inherited cardiomyopathies, nephrotic syndrome, familial hypercholesterolemia, stroke, or any thromboembolic disorder • Unhealed fracture as defined by orthopedic opinion • Symptoms associated with skull abnormalities such as basilar invagination, basilar impression or Chiari malformation • Prior treatment with anti-sclerostin antibody, fluoride or strontium, parathyroid hormone (PTH) within 12 months prior to screening, denosumab within 12 months or zoledronic acid within 6 months prior to first dose • Less than 2 evaluable vertebrae by DXA evaluation in the region of interest, L1 - L4, as confirmed by the central imaging laboratory. • Clinically significant valvular heart disease based on local echocardiogram (ECHO) results.