Tetrahydrobiopterin (BH4)-deficient hyperphenylalaninemia

An amino acid metabolic disorder that are characterized phenotypically by hyperphenylalaninemia, depletion of the neurotransmitters dopamine and serotonin, and progressive cognitive and motor deficits and that has material basis in autosomal recessive mutations in the genes encoding enzymes involved in the synthesis or regeneration of BH4.