Activated phosphoinositide 3-kinase delta syndrome (APDS) is a rare autosomal dominant primary immunodeficiency disorder caused by heterozygous gain-of-function mutations in the PIK3CD gene, which encodes the p110δ catalytic subunit of the class IA phosphoinositide 3-kinase (PI3Kδ) (1). This evidence concerns the gene PIK3CD and activated PI3K-delta syndrome.