Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Treacher Collins syndrome ?
    ### Response:
    Treacher Collins syndrome (TCS) is a condition that affects the development of bones and other tissues of the face. The signs and symptoms vary greatly, ranging from almost unnoticeable to severe. Most affected people have underdeveloped facial bones, particularly the cheek bones, and a very small jaw and chin (micrognathia).
    