Seven known genetic defects, including Bruton tyrosine kinase (Btk), CD4OL, and signaling lymphocyte activation molecule-associated protein (SAP) (all X-linked) and inducible costimulator molecule (ICOS), transmembrane activator and calcium-modulator and cytophilin ligand interactor (TACI), B-cell-activating factor of the tumor necrosis family receptor (BAFFR), and CD19 (all autosomal recessive), were found in patients with the phenotype of common variable immunodeficiency (CVID).
The results support the notion that the possibility of a SH2D1A gene mutation should be considered in hypogammaglobulinemic male patients before a diagnosis of CVID is made.
We therefore suggest that XLP should be suspected in certain boys previously diagnosed as having CVID and recommend that patients are investigated both by genetic analysis of SH2D1A and by expression of SAP protein.