Quantification of total serum immunoglobulins by nephelometry showed severe hypogammaglobulinemia (Total IgG <140 mg/dL, Total IgA, 2.9 mg/dL; Total IgM <5 mg/dL) with an electrophoresis protein value compatible with agammaglobulinemia. Here, CD40LG is linked to agammaglobulinemia.