A Non-Interventional Interview Study of Phenylketonuria (PKU) Adults

Inclusion Criteria: Patients eligible to participate in this study must meet all of the following criteria: 1. ≥18 and ≤70 years of age at the time of consent; 2. Clinically-confirmed diagnosis of Phenylketonuria (PKU); 3. Blood Phe test completed within eight weeks prior to screening date or blood Phe test completed within eight weeks post screening date; 4. Able to read, understand, and speak fluently the language(s) of their designated country sufficiently to participate in an interview and/or complete all assessments; 5. Willing and able to participate in a telephone interview lasting approximately 90 minutes; 6. Willing to be audio-recorded during the interview session; 7. Willing and able to provide written informed consent indicating that they understand the purpose and procedures required for the study and are willing to participate. Exclusion Criteria: Patients meeting any of the following criteria will not be included in the study: 1. Currently pregnant; 2. Current or previous exposure to pegvaliase treatment or participation in a pegvaliase clinical trial; 3. Has a significant cognitive impairment, hearing difficulty, visual impairment, acute psychopathology, medical condition, or insufficient knowledge of the interview language that, in the opinion of the investigator or interviewer, would interfere with his or her ability to provide written consent and participate/complete an interview.