Background The long-term clinical course and closely related biomarkers in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with anti-neurofascin 155 (NF155) antibodies remain to be elucidated. Methods We retrospectively studied the longitudinal clinical courses of three Japanese male anti-NF155 antibody-positive CIDP patients. Anti-NF155 antibody levels were measured by flow cytometry using HEK293 cell lines stably expressing human NF155. Results All three patients presented with chronic progressive sensorimotor disturbance, with ages at onset of 16, 26, and 34 years old, and they were followed for 58, 31, and 38 months, respectively, from the onset. All patients had postural tremor and generalized decreased deep tendon reflexes. Peak cerebrospinal fluid protein levels were > 400 mg/dl, and nerve conduction studies (NCS) showed severe demyelination patterns. Combined immunotherapies including intravenous immunoglobulin, plasma exchange, corticosteroids, and other immunosuppressants ameliorated clinical severity and NCS abnormalities, with improvements of > 10 kg in grip strength and at least 20% in F-wave latencies. However, their symptoms exacerbated after the immunotherapies were tapered. Anti-NF155 antibody levels varied in parallel with the clinical and electrophysiological changes, or preceded them. Conclusion The patients’ clinical courses suggest that anti-NF155 antibody levels and NCS findings could be disease activity markers in anti-NF155 antibody-positive CIDP.
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