When do you consider testing autoimmune antibodies for axonal polyneuropathies without clear etiology?

Dr. @Dr. First Last gave an excellent summary of the clinical red flags that should trigger antibody testing in polyneuropathies. I would like to highlight that not all antibodies are pathogenic or cause the same phenotypes/clinical syndromes; therefore, I would like to break it down by antibody group:

Group 1: Non-specific antibodies associated with connective tissue diseases (ANA, SSA, SSB, ANCA, RF, dsDNA, etc.)

Group 2: Paraneoplastic antibodies (Hu, CV2/CRMP5, etc)

Group 3: Ganglioside anti...

Testing for autoimmune antibodies in axonal polyneuropathies without a clear etiology is considered when the clinical picture, history, or associated features suggest an underlying immune-mediated or paraneoplastic process. Here’s when it would be reasonable to consider antibody testing:

1. Subacute Onset or Rapid Progression

Faster-than-expected progression (weeks to a few months) is suspicious for an immune-mediated cause rather than a classic length-dependent axonal neuropathy from metabolic ...