Amyloid-like IgM deposition neuropathy with multiple mononeuropathies and generalized neuropathy.

Amyloid-like IgM deposition neuropathy is a distinct entity in the setting of IgM monoclonal gammopathy in which endoneurial perivascular entire IgM-particle accumulation leads to a painful sensory followed by motor peripheral neuropathy. We report a 77-year-old man presenting with progressive multiple mononeuropathies starting with painless right foot drop. Electrodiagnostic studies showed severe axonal sensory-motor neuropathy superimposed by multiple mononeuropathies. Laboratory investigations were remarkable for biclonal gammopathy of IgM kappa, IgA lambda and severe sudomotor and mild cardiovagal autonomic dysfunction. A right sural nerve biopsy showed multifocal axonal neuropathy, prominent microvasculitis, and prominent large endoneurial deposits of Congo-red negative amorphous material. Laser dissected mass spectrometry-based proteomics identified IgM kappa deposit without serum amyloid-P protein. This case has several distinctive features, including motor preceding sensory involvement, prominent IgM-kappa proteinaceous deposits replacing most of the endoneurium, a prominent inflammatory component, and improvement of motor strength after immunotherapy. Copyright © 2023 Elsevier B.V. All rights reserved.

Citation

Pannathat Soontrapa, Christopher J Klein, P James B Dyck, Sarah E Berini, Ellen D McPhail, Moritz Binder, Pitcha Chompoopong, JaNean Engelstad, Kamal Shouman. Amyloid-like IgM deposition neuropathy with multiple mononeuropathies and generalized neuropathy. Neuromuscular disorders : NMD. 2023 May;33(5):391-395

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PMID: 37028153

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