Hyperphenylalaninemia, Bh4-Deficient, D, also known as hyperphenylalaninemia with primapterinuria, is related to hyperphenylalaninemia, bh4-deficient, a. An important gene associated with Hyperphenylalaninemia, Bh4-Deficient, D is PCBD1 (Pterin-4 Alpha-Carbinolamine Dehydratase 1). Related phenotypes are hyperphenylalaninemia and abnormal circulating biopterin concentration