Below is an instruction from Human. Write a response.
    ### Instruction:
    How to diagnose Koolen de Vries syndrome ?
    ### Response:
    How is 17q21.31 microdeletion syndrome diagnosed? 17q21.31 microdeletion syndrome is diagnosed in individuals who have a deletion of 500,000 to 650,000 DNA building blocks (base pairs) at chromosome 17q21.31. The diagnosis can be made by various genetic testing methods, including FISH and array CGH.
    