ORIGINAL COMMUNICATION Plasma exchanges for severe acute neurological deterioration in patients with IgM anti-myelin-associated glycoprotein (anti- MAG) neuropathy M. Baron 1 • P. Lozeron 2 • S. Harel 1 • D. Bengoufa 3 • M. Vignon 1 • B. Asli 1 • M. Malphettes 4 • N. Parquet 5 • A. Brignier 5 • J. P. Fermand 1 • N. Kubis 2 • Bertrand Arnulf 1,6 Received: 18 December 2016 / Revised: 20 March 2017 / Accepted: 18 April 2017 Ó Springer-Verlag Berlin Heidelberg 2017 Abstract Monoclonal IgM anti-myelin-associated glyco- protein (MAG) antibody-related peripheral neuropathy (anti-MAG neuropathy) is predominantly a demyelinating sensory neuropathy with ataxia and distal paresthesia. The clinical course of anti-MAG neuropathy is usually slowly progressive making difficult the identification of clear cri- teria to start a specific treatment. Although no consensus treatment is yet available, a rituximab-based regimen tar- geting the B-cell clone producing the monoclonal IgM may be proposed, alone or in combination with alkylating agents or purine analogs. However, in some rare cases, an acute and severe neurological deterioration can occur in few days leading to a rapid loss of autonomy. In these cases, a treatment rapidly removing the monoclonal IgM from the circulation might be useful before initiating a specific therapy. We report successful treatment with plasma exchanges (PE) in four patients presenting with acute neurological deterioration. PE allowed a dramatic and rapid neurological improvement in all patients. PE are safe and may be useful at the initial management of these cases of anti-MAG neuropathy. Keywords Anti-MAG neuropathy Á Acute deterioration Á Plasma exchanges Introduction Monoclonal IgM (monoclonal IgM) anti-myelin-associated glycoprotein (MAG) antibody-related peripheral neuropathy (anti-MAG neuropathy) represents up to 70% of IgM-asso- ciated peripheral neuropathy. Anti-MAG neuropathy is an entity characterized by a demyelinating sensory neuropathy with ataxia, tremor, distal paresthesia but little motor involvement [1, 2]. Electroneuromyography (ENMG) demonstrates demyelinating features with prolonged distal latencies and reduced distal sensory conduction velocity [2]. The serum monoclonal IgM is usually associated with an IgM producing B-cell clone without detectable lym- phoid proliferation referred as monoclonal gammopathy of unknown significance. However, in up to 35% of cases, an overt lymphoplasmacytic bone-marrow involvement referred as Waldenstrom macroglobulinemia (WM) or an indolent B-cell lymphoma is present. Whatever the size of the B-cell clone, patients with anti- MAG neuropathy usually have a progressive course which may lead to severe disabling sensory and to a lesser extend motor symptoms. Therefore, a specific treatment needs to be started before irreversible axonal loss. However, criteria required to initiate the treatment are difficult to establish given the usually slowly progressing disease, the hetero- geneity of the outcome, and the unstandardized endpoints measurement [3]. & Bertrand Arnulf Bertrand.arnulf@aphp.fr 1 De´partement d’Immuno-He´matologie, APHP, Hoˆpital Saint Louis, Paris, France 2 Service de Physiologie Clinique-Explorations Fonctionnelles, AP-HP, Hoˆpital Lariboisie`re, INSERM UMR965, Universite´ Paris Diderot, Sorbonne Paris Cite´, Paris, France 3 Laboratoire d’Immunologie et Histocompatibilite´, APHP, Hoˆpital Saint Louis, Paris, France 4 De´partement d’Immunologie clinique, APHP, Hoˆpital Saint Louis, Paris, France 5 De´partement d’Aphe´re`se the´rapeutique, APHP, Hoˆpital Saint Louis, Paris, France 6 Department of Immunology, Saint Louis Hospital, 1 Avenue Claude Vellefaux, 75010 Paris, France 123 J Neurol DOI 10.1007/s00415-017-8502-3