Phenylketonuria

Phenylketonuria is an inherited disorder in which impaired phenylalanine metabolism raises blood phenylalanine. Without treatment, excess phenylalanine can damage the developing brain.

Phenylalanine hydroxylase: An enzyme that converts phenylalanine into tyrosine using tetrahydrobiopterin as a cofactor. Most classic cases result from reduced activity of this enzyme.
Newborn screening: Testing shortly after birth to identify conditions that benefit from early intervention. Early detection allows treatment before phenylalanine damages the developing brain.
Asbjørn Følling: Norwegian physician who identified phenylketonuria in 1934 by detecting phenylketones in patients’ urine. His investigation first connected the distinctive urine finding with intellectual disability.
Tyrosinemia: A group of inherited disorders in which tyrosine breakdown is impaired. It affects the same amino-acid pathway but causes a different metabolic disease.
PAH gene: A gene that encodes phenylalanine hydroxylase. Pathogenic variants in this gene cause most cases of phenylketonuria.
Low-phenylalanine diet: A diet that limits phenylalanine while supplying enough protein and essential nutrients. Dietary phenylalanine restriction is the mainstay of treatment.
Phenylketonuria screening test: A newborn blood test that measures phenylalanine to detect phenylketonuria. The test made presymptomatic diagnosis possible at population scale.
Alkaptonuria: An inherited disorder caused by impaired breakdown of homogentisic acid in tyrosine metabolism. It is another amino-acid metabolic disorder, but its defect lies downstream.
Tetrahydrobiopterin: A cofactor required by enzymes including phenylalanine hydroxylase. Defects in its production or recycling can also impair phenylalanine breakdown.
Medical food: A specially formulated food product designed to meet nutritional needs in a medical condition. Protein substitutes provide amino acids while minimizing phenylalanine intake.

Linked from 12 pages