Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to Legg-Calv-Perthes disease ?
    ### Response:
    Legg-Calv-Perthes disease is usually not caused by genetic factors. The cause in these cases is unknown. In a small percentage of cases, mutations in the COL2A1 gene cause the bone abnormalities characteristic of Legg-Calv-Perthes disease. The COL2A1 gene provides instructions for making a protein that forms type II collagen.
    