Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) tetrasomy 18p ?
    ### Response:
    Tetrasomy 18p is a chromosomal condition that affects many parts of the body. This condition usually causes feeding difficulties in infancy, delayed development, intellectual disability that is often mild to moderate but can be severe, changes in muscle tone, distinctive facial features, and other birth defects.
    