In contrast to CVID, XLA is caused by a congenital defect of B cell development and most often presents during infancy after maternal Igs have dissipated, however, there have been several cases previously described in which individuals had late onset of chronic infection or were misdiagnosed with CVID and later found to have Btk mutations [2,3]. This evidence concerns the gene BTK and Bruton-type agammaglobulinemia.