Hyperphenylalaninemia, Bh4-Deficient, C, also known as dihydropteridine reductase deficiency, is related to hyperphenylalaninemia and phenylketonuria, and has symptoms including seizures and tremor. An important gene associated with Hyperphenylalaninemia, Bh4-Deficient, C is QDPR (Quinoid Dihydropteridine Reductase). Affiliated tissues include heart and skin, and related phenotypes are intellectual disability and dysphagia