PIK3CD and activated PI3K-delta syndrome: Trio whole exome sequencing (WES) was pursued and revealed a heterozygous de novo missense variant in phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit δ (PIK3CD) (NM_005026.3, c.3061G > A, p.E1021K) the most common mutation previously reported in association with APDS [5].