Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) hereditary hypophosphatemic rickets ?
    ### Response:
    Hereditary hypophosphatemic rickets is a disorder related to low levels of phosphate in the blood (hypophosphatemia). Phosphate is a mineral that is essential for the normal formation of bones and teeth.  In most cases, the signs and symptoms of hereditary hypophosphatemic rickets begin in early childhood.
    