Post Marketing Surveillance Study to Observe Safety and Effectiveness of CRYSVITA® in S. Korean Patients

Inclusion Criteria: 1. Patients who have been started on CRYSVITA® in accordance with the approved label in Korea 2. Those (or his/her legal guardian) who have agreed in writing to participate in the survey. Children who have obtained a written consent of his/her legal guardian about participation in this survey. In case of pediatric patient, explain sufficiently what you think the patient can understand. In this case, the legal guardian may provide supplementary explanations of the survey. Exclusion Criteria: 1. Patients for whom Burosumab is contraindicated according local label of CRYSVITA® 2. Patients who intend to use this drug for other purposes 3. Patients who participated in pre-market clinical trials with CRYSVITA® (Consecutive investigation method ONLY) 4. Patients who have been taking this drug before the starting day of this study (Consecutive investigation method ONLY)