CD40LG and agammaglobulinemia: A study of the prevalence of hypogammaglobulinemia in 36 patients with giant cell arteritis and polymyalgia rheumatica on glucocorticoid therapy reported that approximately half of the patients developed IgG deficiency with less impact on IgA and IgM and a reduction in naïve B cells with relative preservation of class switched memory B cells (73).