Phenotypic and clinical heterogeneity associated with monoallelic TNFRSF13B−A181E mutations in common variable immunodeficiency

Mutations in the TNFRSF13B (TACI) gene have been reported to be associated with Common Variable ImmunoDeficiency (CVID). Of 48 patients evaluated within the immunodeficiency clinic, 39 had CVID, 6 had symptomatic IgA deficiency (IgAD) with or without IgG2 and IgG4 subclass deficiency, while 3 had unclassified immune dysregulatory disorders. In all 48 patients TACI genetic testing was performed, and monoallelic mutations were observed in 4 of the 39 CVID patients (10.26%), an incidence comparable to other studies. Of the 6 IgAD patients, 1 had a heterozygous TACI mutation (16.67%), while of the 3 unclassified patients, 1 had a monoallelic TACI mutation (33.3%), but his sibling who also had the same mutation had CVID. The A181E mutation is one of the statistically significant, among the known TACI gene mutations. Here, 5 of the 6 patients were found to have the A181E mutation (10.42%), which is higher than previously observed. We also evaluated 114 controls and found the A181E mutation in only 1 individual (0.88%). We report in this study that the A181E mutation is associated with a very heterogeneous clinical presentation along with variability in B-cell numbers and amount of TACI protein on memory B cells.