The prevalence of anti-MAG neuropathy is estimated to be between 0.45 and 1.2 per 100,000, with the lower number based on a survey in Southern England,7and the latter from epidemiologic studies reporting a prevalence of IgM monoclonal gammopathy of 51 per 100,000,8with 5.4% of Waldenström's patients experiencing neuropathy,9and approximately 50% of IgM proteins of patients with neuropathy exhibiting anti-MAG antibody activity.10In a large study of 202 patients, the male-to-female ratio was 1.9 to 1, with a mean age of symptom onset of 62.6 years (range 25-91).11 Here, CD40LG is linked to neuropathy.