Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Koolen de Vries syndrome ?
    ### Response:
    Koolen de Vries syndrome, formerly known as 17q21.31 microdeletion syndrome, is a condition caused by a small deletion of genetic material from chromosome 17. The deletion occurs at a location designated as q21.31. People with 17q21.31 microdeletion syndrome may have developmental delay, intellectual disability, seizures, hypotonia.
    