Approximately 600 pediatric patients prescribed Humira Injection in usual practice according to the approved Korean product label will be registered into this observational study. Baseline data will be obtained at enrollment including demographics, underlying diseases and complications especially in regard to purified protein derivative (PPD) skin test, and chest X-ray. At routine visits for Humira Injection administration, which will occur according to usual medical practice, concomitant medication information and adverse events information will be collected for up to 70 days after the last administration of Humira.