Background Heterozygous point mutations in the GT splice donor consensus sequence of exon 11 of the PIK3R1 gene (coding for p85α, p55α, and p50α regulatory subunits of PI3K) lead to exon skipping and thereby to an aberrant protein that leaves PI3K hyperactivated. Several patients with this particular variant of PI3 kinase delta syndrome (APDS) suffering from sinopulmonary infections and lymphoproliferation have been described.

Methods (Whole exome) sequencing, evaluation of cellular and clinical phenotypes.

Results We here report a family with a new heterozygous mutation in this gene, a 9 bp deletion (c.1418_1425+1del) that, however, leads to the same skipping of exon 11. The clinical phenotypes of their members partly overlap features of patients of other reports.

Conclusions We found a new mutation in PIK3R1 and show how broad the resulting clinical spectrum can be.