X-ray of a child with a disease known as osteogenesis imperfecta type III with progressive deformities in the lower extremities, together with severe osteoporosis, fragile bones, and coxa vara. Left femoral shaft fracture is seen with pseudarthrosis formation. Osteogenesis imperfecta (OI) is an inherited (genetic) bone disorder that is present at birth. It is also known as brittle bone disease. A child born with OI may have soft bones that break (fracture) easily, bones that are not formed normally, and other problems. Signs and symptoms may range from mild to severe.