Letter to the EditorAltered germinal center reaction and abnormal B cell peripheral maturation in PI3KR1-mutated patients presenting with HIGM-like phenotype

•Eight patients with PIK3R1 gain of function mutations have been reported to date.•We have identified 4 novel unrelated patients to be mutated in PIK3R1.•PIK3R1 mutated patients present early peripheral B cell arrest.•PIK3R1 mutations alter the GC reaction resembling AID deficiency.•Poor growth emerges as an accompanying feature of this disorder.