Idiopathic Multicentric Castleman Disease Presenting as Recurrent Acute-Onset Demyelinating Neuropathy

A 53-year-old man presented with recurrent, motor-predominant acute polyneuropathy that progressed to a loss of ambulation, accompanied by fever and arthralgia. Nerve conduction studies demonstrated demyelinating features, a cerebrospinal fluid analysis revealed albuminocytological dissociation, and the presence of anti-GM1/GM2 IgM antibodies suggested acute inflammatory neuropathy. Further evaluation revealed markedly elevated interleukin-6 (IL-6) levels and diffuse lymphadenopathy on FDG-PET imaging, and a subsequent lymph node biopsy confirmed idiopathic multicentric Castleman disease (iMCD). While slowly progressive sensory neuropathy is the typical manifestation of iMCD, acute, severe, motor-predominant neuropathy is extremely rare. This case highlights the mechanisms of IL-6-mediated neuropathy.