Question: How to diagnose Koolen de Vries syndrome ?
Answer: 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. This condition cannot be diagnosed by traditional chromosome tests (karyotype) that look at chromosome banding patterns under the microscope because the deletion is too small to be detected.
Source: GARD