Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Langerhans cell histiocytosis ?
    ### Response:
    Langerhans cell histiocytosis (LCH) is a disorder that primarily affects children, but is also found in adults of all ages. People with LCH produce too many Langerhans cells or histiocytes, a form of white blood cell found in healthy people that is supposed to protect the body from infection.
    