Mepolizumab Long-term Study to Assess Real World Safety and Effectiveness of Eosinophilic Granulomatosis With Polyangiitis (EGPA) in Japan

Inclusion Criteria: * Adult participants with EGPA of \>=20 years of age inclusive, at the time of signing the informed consent. * Participants must have a current clinical diagnosis of EGPA by physician. * Participants have continuously used NUCALA for at least 96 weeks for the treatment of EGPA as mentioned in the current label in Japan. • Participants thus were registered and completed the NUCALA PMS study (special drug use investigation; Protocol Number 208505, NCT03557060) prior to be enrolled in this study. * Physician's decision to continue treatment with NUCALA for the treatment of EGPA as mentioned in the current label in Japan. * Prior to commencing any study related activities, participants must be able and willing to provide written informed consent. Exclusion Criteria: * Participants who have previously discontinued NUCALA treatment for EGPA for more than 12 weeks. * Participating in another clinical trial within the past 12 months, in which the participant has been exposed to an investigational or non-investigational pharmaceutical product. * Participants with any reasons that in physician's opinion would place the participants at risk. * Participants who are pregnant or breastfeeding.