Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Hypophosphatemic rickets ?
    ### Response:
    What causes hypophosphatemic rickets? Hypophosphatemic rickets is almost always hereditary and may be caused by mutations in any of several genes. The specific gene involved determines the way it is inherited. Most commonly, it is caused by a mutation in the PHEX gene.
    