The lower sensitivity of our method and the fact that we carried out serum immunofixation only in those patients who had an abnormal protein electrophoresis could explain why the proportion of IgM-secreting DLBCL in our series was somewhat lower compared to that with an abnormal IgMκ/IgMλ ratio described by Jardin et al. [17]. The gene discussed is CD40LG; the disease is diffuse large B-cell lymphoma.