Activated phosphoinositide 3-kinase δ syndrome type 1 (APDS1) is a rare disease caused by gain-of-function (GOF) mutations in the PIK3CD gene that presents with combined immunodeficiency due to decreases in IgA, IgG, naive CD4 and naive CD8 cells. Nearly all APDS1 patients suffer from recurrent respiratory tract infections with most presenting with bronchiectasis and chronic viral infections.