phenylketonuria(n = noun.state) pku - a genetic disorder of metabolism; lack of the enzyme needed to turn phenylalanine into tyrosine results in an accumulation of phenylalanine in the body fluids which causes various degrees of mental deficiency;
is a kind of inborn error of metabolism

phenylketonuria, n. an inherited inability to metabolize phenylalanine, ultimately leading to mental deficiency if untreated.

Etymology:
PHENYL + KETONE + -URIA