PIK3R1 and cancer: In the aforementioned individual described with features of APDS2 and MCAP, the pathogenic heterozygous PIK3R1 variant, p.(Asn564Lys), was associated with mildly increased lymphocyte AKT phosphorylation.18 A different missense change at codon 564, p.(Asn564Asp), was the most frequently detected variant in our vascular malformation and overgrowth cohort and is also described in cancer.