Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Familial hyperinsulinism ?
    ### Response:
    Familial hyperinsulinism is an inherited condition that causes individuals to have abnormally high levels of insulin, which leads to frequent episodes of low blood sugar (hypoglycemia). In infants and young children, these episodes are characterized by a lack of energy (lethargy), irritability, and/or difficulty feeding.
    