Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Kleefstra syndrome ?
    ### Response:
    Kleefstra syndrome is a disorder that involves many parts of the body. Characteristic features of Kleefstra syndrome include developmental delay and intellectual disability, severely limited or absent speech, and weak muscle tone (hypotonia). Affected individuals also have an unusually small head size (microcephaly) and a wide, short skull (brachycephaly).
    