Diabetes Mellitus Is a Possible Risk Factor for Nodo-paranodopathy With Antiparanodal Autoantibodies.

BACKGROUND AND OBJECTIVES: Nodo-paranodopathies are peripheral neuropathies with dysfunction of the node of Ranvier. Affected patients who are seropositive for antibodies against adhesion molecules like contactin-1 and neurofascin show distinct clinical features and a disruption of the paranodal complex. An axoglial dysjunction is also a characteristic finding of diabetic neuropathy. Here, we aim to investigate a possible association of antibody-mediated nodo-paranodopathy and diabetes mellitus (DM). METHODS: We retrospectively analyzed clinical data of 227 patients with chronic inflammatory demyelinating polyradiculoneuropathy and Guillain-Barré syndrome from multiple centers in Germany who had undergone diagnostic testing for antiparanodal antibodies targeting neurofascin-155, pan-neurofascin, contactin-1-associated protein 1, and contactin-1. To study possible direct pathogenic effects of antiparanodal antibodies, we performed immunofluorescence binding assays on human pancreatic tissue sections. RESULTS: The frequency of DM was 33.3% in seropositive patients and thus higher compared with seronegative patients (14.1%, OR = 3.04, 95% CI = 1.31-6.80). The relative risk of DM in seropositive patients was 3.4-fold higher compared with the general German population. Seropositive patients with DM most frequently harbored anti-contactin-1 antibodies and had higher antibody titers than seropositive patients without DM. The diagnosis of DM preceded the onset of neuropathy in seropositive patients. No immunoreactivity of antiparanodal antibodies against pancreatic tissue was detected. DISCUSSION: We report an association of nodo-paranodopathy and DM. Our results suggest that DM may be a potential risk factor for predisposing to developing nodo-paranodopathy and argue against DM being induced by the autoantibodies. Our findings set the basis for further research investigating underlying immunopathogenetic connections.

Antiparanodal antibodies and IgG subclasses in acute autoimmune neuropathy.

OBJECTIVE: To determine whether IgG subclasses of antiparanodal autoantibodies are related to disease course and treatment response in acute- to subacute-onset neuropathies, we retrospectively screened 161 baseline serum/CSF samples and 66 follow-up serum/CSF samples. METHODS: We used ELISA and immunofluorescence assays to detect antiparanodal IgG and their subclasses and titers in serum/CSF of patients with Guillain-Barré syndrome (GBS), recurrent GBS (R-GBS), Miller-Fisher syndrome, and acute- to subacute-onset chronic inflammatory demyelinating polyradiculoneuropathy (A-CIDP). We evaluated clinical data retrospectively. RESULTS: We detected antiparanodal autoantibodies with a prevalence of 4.3% (7/161), more often in A-CIDP (4/23, 17.4%) compared with GBS (3/114, 2.6%). Longitudinal subclass analysis in the patients with GBS revealed IgG2/3 autoantibodies against Caspr-1 and against anti-contactin-1/Caspr-1, which disappeared at remission. At disease onset, patients with A-CIDP had IgG2/3 anti-Caspr-1 and anti-contactin-1/Caspr-1 or IgG4 anti-contactin-1 antibodies, IgG3 being associated with good response to IV immunoglobulins (IVIg). In the chronic phase of disease, IgG subclass of one patient with A-CIDP switched from IgG3 to IgG4. CONCLUSION: Our data (1) confirm and extend previous observations that antiparanodal IgG2/3 but not IgG4 antibodies can occur in acute-onset neuropathies manifesting as monophasic GBS, (2) suggest association of IgG3 to a favorable response to IVIg, and (3) lend support to the hypothesis that in some patients, an IgG subclass switch from IgG3 to IgG4 may be the correlate of a secondary progressive or relapsing course following a GBS-like onset.

Anti-pan-neurofascin IgG3 as a marker of fulminant autoimmune neuropathy.

OBJECTIVE: To identify and characterize patients with autoantibodies against different neurofascin (NF) isoforms. METHODS: Screening of a large cohort of patient sera for anti-NF autoantibodies by ELISA and further characterization by cell-based assays, epitope mapping, and complement binding assays. RESULTS: Two different clinical phenotypes became apparent in this study: The well-known clinical picture of subacute-onset severe sensorimotor neuropathy with tremor that is known to be associated with IgG4 autoantibodies against the paranodal isoform NF-155 was found in 2 patients. The second phenotype with a dramatic course of disease with tetraplegia and almost locked-in syndrome was associated with IgG3 autoantibodies against nodal and paranodal isoforms of NF in 3 patients. The epitope against which these autoantibodies were directed in this second phenotype was the common Ig domain found in all 3 NF isoforms. In contrast, anti-NF-155 IgG4 were directed against the NF-155-specific Fn3Fn4 domain. The description of a second phenotype of anti-NF-associated neuropathy is in line with some case reports of similar patients that were published in the last year. CONCLUSIONS: Our results indicate that anti-pan-NF-associated neuropathy differs from anti-NF-155-associated neuropathy, and epitope and subclass play a major role in the pathogenesis and severity of anti-NF-associated neuropathy and should be determined to correctly classify patients, also in respect to possible differences in therapeutic response.