Which disorder is caused by autosomal recessive deficiency in hepatic phenylalanine hydroxylase leading to cognitive and language delays, with newborn Guthrie screening detectable?

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Phenylketonuria is an autosomal recessive metabolic disorder caused by a deficiency of hepatic phenylalanine hydroxylase, the enzyme that converts phenylalanine to tyrosine. When this enzyme is missing or defective, phenylalanine builds up in the blood and brain, leading to cognitive and language delays if not treated early. Newborn Guthrie screening detects elevated phenylalanine levels, enabling prompt dietary management to prevent intellectual disability; treatment typically involves a strict low-phenylalanine diet and ensuring adequate tyrosine, which becomes essential. Other conditions like Down syndrome, Angelman syndrome, and Fragile X syndrome arise from chromosomal or gene mechanisms with different inheritance patterns and are not identified by this newborn metabolic screen.