Hyperphenylalaninemia, Bh4-Deficient, a, also known as 6-pyruvoyl-tetrahydropterin synthase deficiency, is related to tetrahydrobiopterin deficiency and depressive disorder, and has symptoms including ataxia, muscle rigidity and seizures. An important gene associated with Hyperphenylalaninemia, Bh4-Deficient, a is PTS (6-Pyruvoyltetrahydropterin Synthase), and among its related pathways/superpathways are Metabolism and Regulation of expression of SLITs and ROBOs. The drugs Diazepam and Doxazosin have been mentioned in the context of this disorder. Affiliated tissues include brain and prefrontal cortex, and related phenotypes are hypotonia and opisthotonus