Final answer:
Sensorineural deafness is not a typical clinical feature of phenylketonuria; the other options listed are associated with PKU to varying degrees. (option a)
Step-by-step explanation:
The clinical feature that is not typically associated with phenylketonuria (PKU) is sensorineural deafness. Phenylketonuria is a result of a deficiency in the enzyme phenylalanine hydroxylase, which is critical for metabolizing the amino acid phenylalanine to tyrosine. When phenylalanine accumulates in the body, it can result in a number of clinical features, including a characteristic "mousy" odor due to the buildup of phenylalanine metabolic byproducts, light hair and skin pigmentation as tyrosine is also a precursor for melanin, microcephaly, and possibly infantile spasms. However, sensorineural deafness is not commonly listed as a feature of PKU.
Hence, the answer is option a