Distinct lymphocytes subsets in IgM-related neuropathy: clinical-immunological correlations.

IgM-related neuropathy generally presents as a late-onset demyelinating polyneuropathy with predominant sensory loss and ataxia. However, we recently reported the clinical, neurophysiological and pathological findings from our cohort and identified in about a third of patients an atypical phenotype. We analyzed by flow cytometry the different lymphocytes subsets in the peripheral blood of patients affected by IgM-related neuropathy, chronic inflammatory demyelinating polyneuropathy (CIDP), monoclonal gammopathy of undetermined significance and healthy subjects, to investigate whether different immunological patterns may differentiate the classical phenotype from atypical forms. IFN-gamma producing CD4+ and CD8+ T lymphocytes, as well as CD4+ and CD8+ T cells expressing T-bet (T-helper type 1, Th1) were increased in CIDP patients. The percentage of circulating CD4+ and CD8+ T cells producing IL-10 as well as the percentage of CD19+ cells expressing Blimp-1 were higher in patients with IgM-neuropathy. We did not find any significant differences in the different lymphocytes subsets in the IgM-related neuropathy between patients with classical and atypical phenotype. Th1 cells are increased in CIDP patients while a T helper type 2-phenotype seems to prevail in patients with IgM-neuropathy. Further studies involving a larger patient population are needed to evaluate if different lymphocytes subset may be involved in different clinical phenotypes of IgM-related neuropathy.