PIK3CD and activated PI3K-delta syndrome: Although the PIK3CD mutation c.3061G > A (this mutation was not found in the normal population) detected in one of our patients has not been reported to be a pathogenic site of CAEBV, the gain-of-function mutation of PIK3CD was confirmed to be related to the pathogenesis of activated PI3 kinase delta syndrome (APDS), which is a primary immunodeficiency and can lead to EBV infection [20, 21].