Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) spondylothoracic dysostosis ?
    ### Response:
    Spondylothoracic dysostosis is a condition characterized by the malformation of the bones of the spine and ribs. The bones of the spine (vertebrae) do not develop properly, which causes them to be misshapen and abnormally joined together (fused). The ribs are also fused at the part nearest the spine (posteriorly), which gives the rib cage its characteristic fan-like or "crab" appearance in x-rays.
    