Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) aspartylglucosaminuria ?
    ### Response:
    Aspartylglucosaminuria is a condition that causes a progressive decline in mental functioning.  Infants with aspartylglucosaminuria appear healthy at birth, and development is typically normal throughout early childhood. The first sign of this condition, evident around the age of 2 or 3, is usually delayed speech.
    