Progressive severe B cell and NK cell deficiency with T cell senescence in adult CD40L deficiency

•CD40 Ligand deficiency may result in severe B and NK loss over time.•T cell senescence is a novel finding in adult CD40 Ligand deficiency.•Long term follow-up of CD40 Ligand deficiency may reveal novel immunological findings.•CD40 Ligand deficient patients not undergoing HSCT should be closely monitored.