A primary immunodeficiency disease in which the cause of the disease is a mutation in PIK3R1 gene. It is characterized by infantile or childhood onset of recurrent bacterial respiratory tract infections, lymphoproliferation, variable antibody deficiency (sometimes with hyper IgM), chronic viral infection (EBV, CMV), and autoimmunity. The disease is MONDO_0014453 (immunodeficiency 36 with lymphoproliferation). Also known as: APDS2, IMD36, activated PI3K-delta syndrome-2, immunodeficiency 36, immunodeficiency type 36.