Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Osteogenesis imperfecta ?
    ### Response:
    Osteogenesis imperfecta (OI) is a group of genetic disorders that mainly affect the bones. People with this condition have bones that break easily, often from little or no trauma. Severity varies among affected people. Multiple fractures are common, and in severe cases, can even occur before birth.
    