<prompt> Answer this question truthfullyCould you please provide me the exact sentence that needs rephrasing? The sentence What is Fragile X syndrome? is already proper English. It is a question in the correct grammatical format.  <response>: <reason> Fragile X syndrome must be differentiated from other diseases that cause mental retardation, change in stature, and increase in testicular size, such as sotos syndrome, Prader-willi syndrome and klinefelter syndrome. 