PIK3R1 Mutation Associated with Hyper IgM (APDS2 Syndrome): A Case Report and Review of the Literature

Background and Objective: APDS [Activated phosphoinositide 3-kinase (PI3K) 6 Syndrome] is a newly found special fonn of primary immunodeficiency caused by mutations in genes encoding PI3K6 subunits and over-activation of the PI3K signaling pathway. Gain-of-function and loss-of-function mutations in PIK3CD (encoding P1106) and PIK3R1 (encoding p85a., p55ct and p50a) lead to APDS1 and APDS2, respectively. The subsequent irregular PI3K downstream signaling cascade is associated with abnormalities in B cells and T cells and the consequent heterogeneous clinical manifestations including respiratory tract infections, autoimmunity, lymphoproliferation and not to mention primary antibody deficiency. In this study, we report a 12-year-old girl with a mutation in the PIK3R1 gene who manifested immunological phenotypes resembling hyper IgM syndrome along with a review of the literature of the previously reported patients. Methods: Whole exome sequencing was performed to detect the underlying genetic mutation in this patient. Results: A tie noco heterozygous splice site mutation in the hot spot of the PK3R1 gene within the intron 10 was found (c.1425,IG>A), Conclusion: Further investigations are required for evaluation of the underlying genetic defects and the possible associations between genetic underpinning and heterogeneous severity and features of the disease.