Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is an inherited disorder of connective tissue. In most cases, a heterozygous mutation in COL1A1 or COL1A2 leads to abnormal or inadequate type I collagen, the major structural protein in bone. Other OI-related genes can produce similar phenotypes. Bone is not simply a hard mineral block. Its strength depends on an organised collagen framework that gives mineral a stable structure. When that framework is abnormal, bones can fracture with forces that would not injure typical bone. Repeated fractures may cause pain, reduced mobility, bowing of long bones, and progressive skeletal deformity. Vertebral compression can contribute to height loss and spinal curvature. Type I collagen is also present outside bone. This explains why OI may be accompanied by blue or grey-blue sclerae, dentinogenesis imperfecta, hearing loss, ligamentous laxity, and short stature. The clinical range is broad: one person may have several fractures with few visible skeletal changes, while another may have fractures, deformity, and substantial functional limitation from early childhood. Fragility changes how care is delivered. A routine transfer, repositioning manoeuvre, or attempt to pull a limb through...