Short ReportLong-standing Multifocal Motor Neuropathy Presenting With Delayed Clinical Features of Anti–Myelin-Associated Glycoprotein Neuropathy and Elevated Anti–Myelin-Associated Glycoprotein Antibody TitersBernardo, Katrina A. MD*; Weiss, Michael D. MD†Author Information *Department of Neurology, New York University Long Island School of Medicine, Mineola, NY; and †Department of Neurology, University of Washington Medical Center, Seattle, WA. Reprints: Katrina A. Bernardo, MD, Department of Neurology, New York University Long Island School of Medicine, 1401 Franklin Avenue, Garden City, NY 11530 (e-mail: [email protected]). M. D. Weiss is on the speaker bureau for NuFactor and a consultant for Ra Pharma. The remaining author reports no conflicts of interest. Journal of Clinical Neuromuscular Disease: March 2021 - Volume 22 - Issue 3 - p 169-172 doi: 10.1097/CND.0000000000000334 Buy Metrics Abstract Multifocal motor neuropathy with conduction block (MMN) and anti–myelin-associated glycoprotein (MAG) neuropathy are rare chronic acquired demyelinating neuropathies with distinct clinical and electrophysiological characteristics. These neuropathies are generally not known to coexist. This report describes a patient with long-standing MMN who subsequently developed clinical features of anti-MAG neuropathy. This suggests that subtypes of chronic inflammatory neuropathies may not be sharply defined. In addition, a presentation of MMN with anti-MAG titers may be a prognostic indicator of poor response to standard MMN treatment. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.