BH4-deficient hyperphenylalaninemia A (MONDO_0009863) is an autosomal recessive condition caused by mutation(s) in the PTS gene, encoding 6-pyruvoyl tetrahydrobiopterin synthase. It is characterized by BH4-defecient hyperphenylalanemia, depletion of dopamine and serotonin, and progressive cognitive and motor deficits. Also known as: 6-pyruvoyl tetrahydropterin synthase deficiency, 6-pyruvoyl-tetrahydropterin synthase deficiency, Bh4-deficient hyperphenylalaninemia type A, HPABH4A, PTS deficiency, hyperphenylalaninemia due to 6-pyruvoyltetrahydropterin synthase deficiency, hyperphenylalaninemia, BH4-deficient A, hyperphenylalaninemia, Bh4-deficient, type a.