Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Preauricular sinus ?
    ### Response:
    Preauricular sinus is a common birth defect that may be seen during a routine exam of a newborn. It generally appears as a tiny skin-lined hole or pit, often just in front of the upper ear where the cartilage of the ear rim meets the face. It may occur on one side (unilateral) or both sides (bilateral) of the ear.
    