[Rapidly progressive muscle weakness in anti-myelin associated glycoprotein (MAG) neuropathy successfully treated with intravenous immunoglobulin].

Anti-myelin associated glycoprotein (MAG) neuropathy typically progresses slowly, but rare cases exhibit rapid deterioration. We report an 83-year-old man with a two-year history of paresthesia in both feet and recent-onset gait ataxia who developed rapidly progressive muscle weakness in all four limbs over several days. Nerve conduction studies and positive anti-MAG antibodies confirmed the diagnosis of anti-MAG neuropathy. The patient's muscle weakness improved with intravenous immunoglobulin (IVIg) therapy. This case highlights the existence of atypical anti-MAG neuropathy mimicking chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with a rapid deterioration course and suggests the potential efficacy of IVIg in such presentations.