Owing to persistent hypogammaglobulinemia with recurrent infections (IgG: 680 mg/dl (700–1600); IgA 47 mg/dl (70–400); IgM: 22 mg/dl (40–230)) and poor response to pneumococcal polysaccharide-based vaccine, CVID was diagnosed. The gene discussed is CD40LG; the disease is common variable immunodeficiency.