Anti-NF155 antibody-positive autoimmune nodopathy with myocardial 123I-MIBG scintigraphy abnormality

A 68-year-old man presented with numbness and pain of the hands. Neurological examination revealed distal limb weakness, diminished tendon reflexes, sensory disturbances in all extremities, tremors, ataxia, and orthostatic hypotension, which caused repeated fainting spells and falls. The nerve conduction studies revealed definite demyelinating abnormalities. The cerebrospinal fluid protein levels were markedly increased at 638 ‍mg/dl. The contrast-enhanced MRI neurography revealed nerve root enlargement and enhancement, and the 123I-metaiodobenzylguanidine myocardial scintigraphy revealed abnormalities, indicating postganglionic sympathetic small fiber disturbance. This patient was initially diagnosed with a distal acquired demyelinating symmetric type of chronic idiopathic demyelinating polyradiculoneuropathy (CIDP). Intravenous immunoglobulin (IVIg) therapy was nearly ineffective, which was different from typical CIDP, and corticosteroids demonstrated mild efficacy. Five years after his initial visit, anti-neurofascin-155 (NF155) autoimmune nodopathy was suspected based on his pathognomonic symptoms, examination results, and ineffectiveness of IVIg. Anti-NF155-IgG4 antibodies were negative; however, anti-NF155-IgG antibodies tested positive, leading to a final diagnosis of anti-NF155 antibody-positive autoimmune nodopathy. This case highlights the clinical significance of non-IgG4 class anti-NF155-IgG antibodies and the involvement of postganglionic sympathetic small fibers in anti-NF155-IgG-related autoimmune nodopathy.