Patients who have unusually fair complexions can be indicative for phenylketonuria because:

Question

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Tyrosine is a precursor for melanin synthesis, which gives color to the skin, hair, and eyes. In phenylketonuria, the lack of the enzyme phenylalanine hydroxylase leads to the accumulation of phenylalanine and a deficiency of tyrosine. As a result, melanin production is reduced, and patients with phenylketonuria may present with fair complexions.

Patients Who Have Unusually Fair Complexions Can Be Indicative for Phenylketonuria