Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Pallister-Killian mosaic syndrome ?
    ### Response:
    Pallister-Killian mosaic syndrome is a disorder that is characterized by extremely weak muscle tone (hypotonia) in infancy and early childhood, intellectual disability, distinctive facial features, sparse hair, areas of unusual skin coloring (pigmentation), and other birth defects.
    