The Francophone Anti-Mag Cohort: A Clinical Descriptive Study (P3.157)

OBJECTIVE To better characterize clinical, biological, neurophysiological spectrum and response to treatment of patients with monoclonal Ig M gammopathy and anti-myelin-associated glycoprotein (MAG) antibodies titre higher than 1000 Buhlmann® Titre Units. BACKGROUND Polyneuropathy associated with anti-MAG IgM antibodies is a chronic dysimmune demyelinating neuropathy. MAG is a non-compact myelin protein implicated in myelin compaction and axonal maintenance. Anti-MAG neuropathy is usually described as a progressive, predominantly sensitive and length-dependant polyneuropathy with ataxia and sometimes postural tremor. DESIGN/METHODS We retrospectively analysed standardized report forms of 124 patients from nine French speaking neuromuscular centres. RESULTS Mean age of patients at onset was 62.8 years. Mean time to diagnosis and average follow-up were 2.6 and 7.2 years. About one-quarter of patients presented with an unusual clinical phenotype, sometimes evocative of acute or chronic inflammatory demyelinating polyneuropathies. At the most severe stage, one-quarter of patients were significantly disabled. MAG antibody titre was low (< 10 000 BTU), medium (10 000-70 000) or high (≥ 70 000) in 12.9, 50 and 37.1 [percnt] of patients. Diagnosis was MGUS or Waldenstrom disease in 64.5 and 29.8 [percnt] of cases. Fourteen percent of patients did not meet the electrodiagnostic criteria of primary demyelination. Nerve biopsy provided support to the diagnosis of anti-MAG neuropathy in some particular issues (unusual clinical or neurophysiological phenotype, low titres of anti-MAG). Eighty percent of patients received immunotherapy and 43.5 [percnt] were treated with rituximab alone. At 6 month and 7-12 month follow-up, objective clinical responses to rituximab were observed in 35 [percnt] and 31.5 [percnt] of treated patients. Treatment response significantly correlated with shorter disease duration or unusual clinical phenotype with upper limb weakness. CONCLUSIONS Our study highlights the extended spectrum of anti-MAG neuropathy. Further studies are required to confirm factor associated with response to rituximab identified in our cohort. Disclosure: Dr. Svahn has nothing to disclose. Dr. Petiot has nothing to disclose. Dr. Ferraud has nothing to disclose. Dr. Vial has nothing to disclose. Dr. Delmont has nothing to disclose. Dr. Viala has nothing to disclose. Dr. Antoine has nothing to disclose. Dr. Echaniz-Laguna has nothing to disclose. Dr. Kuntzer has nothing to disclose. Dr. Gueguen has received personal compensation for activities with Novartis as a member of the scientific advisory board. Dr. Camdessanche has nothing to disclose.