Other hyperphenylalaninemias

This code represents a group of rare metabolic disorders characterized by elevated phenylalanine levels in the blood, distinct from classical phenylketonuria (PKU). These conditions arise from defects in enzymes or cofactors involved in phenylalanine metabolism, other than phenylalanine hydroxylase deficiency.

Use this code for patients diagnosed with hyperphenylalaninemia that is not classic PKU, such as deficiencies in dihydropteridine reductase (DHPR), 6-pyruvoyl-tetrahydropterin synthase (PTPS), or guanosine triphosphate cyclohydrolase I (GTPCH). Documentation should clearly specify the type of hyperphenylalaninemia or state that it is "other" than PKU, often confirmed by genetic testing or specific enzyme assays.

• Differentiate carefully from E70.0 (Classical Phenylketonuria) based on diagnostic workup and specific enzyme deficiencies.
• Ensure documentation specifies the type of hyperphenylalaninemia when known; otherwise, this "other" code is appropriate.
• Consider sequencing this code as a primary diagnosis when it is the focus of treatment or investigation.