Approximately 10% of CVID patients harbor a mutation in TNFRSF13B (encoding the protein TACI) with a demonstrable biological impact (5), but 1%–2% of the healthy population also carry these variants, causing debate on whether TNFRSF13B mutations should be termed “disease causing” or merely “disease associated”. Here, TNFRSF13B is linked to common variable immunodeficiency.