67 - Autoimmune Peripheral Neuropathies

Abstract

Autoimmune peripheral neuropathies (APNs) occur when immunological tolerance to peripheral nerve components (myelin, axon, or ganglionic neurons) is lost. The most common APNs are acute inflammatory polyneuropathies, such as Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), multifocal motor neuropathy (MMN), immunoglobulin M (IgM)–anti–myelin-associated glycoprotein (MAG) antibody–mediated paraproteinemic neuropathy, and those caused by vasculitis or viral infections. Both cellular and humoral factors, either independently or in concert with each other, appear to play a role, but the specific immune mechanisms have not been fully elucidated. Infectious agents, such as Campylobacter jejuni and Zika virus via molecular mimicry, and now COVID-19, are implicated in some GBS subtypes, but the factors that break tolerance in the other APNs remain unknown. In some acute or chronic APN, antibodies against peripheral nerve glycolipids or glycoproteins are pathogenic and well characterized. Pathogenic IgG4 antibodies against antigens at the nodes of Ranvier that cause disadhesion of nodal and paranodal proteins and conduction block define distinct CIDP subtypes, which respond only to rituximab. Some newly emerging, not pathogenic, autoantibodies more commonly seen in small fiber sensory neuropathies and neuropathic pains are briefly discussed. The current immunotherapies in all APNs are described based on controlled trials or clinical experience.