The purpose of this study was to assess the clinicopathological and therapeutic features of patients with low (≥1000–<10 000 Bühlmann® Titre Units) (BTU), medium (10 000–70 000) or high (≥70 000) anti-Myelin-Associated Glycoprotein (MAG) antibody titres.

We retrospectively and prospectively analysed standardized report forms and medical records of two hundred and two patients from fourteen neuromuscular centres.

Mean age at onset and mean time between symptom onset to last follow-up were respectively 62.6 years (25–91.4) and 8.4 years (0.3–33.3). Anti-MAG antibody titres at diagnosis were low, medium or high in 11, 51 and 38% of patients. Patients presented with monoclonal gammopathy of undetermined significance (MGUS) in 68% of cases. About 17% of patients presented with “atypical” clinical phenotype independently of anti-MAG titres, including acute or chronic sensorimotor polyradiculoneuropathies (12.4%), and asymmetric or multifocal neuropathy (3%). At the most severe disease stage, 22.4% of patients were significantly disabled. Seventy eight percent of patients received immunotherapies. Transient clinical worsening was observed in 12% of patients treated with rituximab (11/92). Stabilisation after rituximab treatment during the 7–12-month follow-up period was observed in 29% of patients. Clinical response to rituximab during the 6-month and/or 7–12-month follow-up period was observed in 31.5% of patients, and correlated with anti-MAG titre ≥10 000BTU. Our study highlights the extended clinical spectrum of patients with anti-MAG neuropathy, which appears unrelated to antibody titre. Besides, it may also suggest beneficial use of rituximab in the early phase of anti-MAG neuropathy.