Paraneoplastic neuronal intermediate filament autoimmunity

Objective: To describe paraneoplastic neuronal intermediate filament (NIF) autoimmunity.
Methods: Archived patient and control serum and CSF specimens were evaluated by tissue-based indirect immunofluorescence assay (IFA). Autoantigens were identified by western blot and mass spectrometry. NIF specificity was confirmed by dual tissue section staining and 5 recombinant NIF-specific HEK293 cell based assays (CBAs, for alpha internexin, neurofilament light [NF-L], medium, or heavy chain, and peripherin). NIF-IgGs were correlated with neurological syndromes and cancers.
Results: Among 65 patients, NIF-IgG positive by IFA and CBAs, 33 were female (51%). Median symptom-onset age was 62 years (range, 18-88). Patients fell into 2 groups, defined by the presence of NF-L-IgG (21 patients, who mostly had ≥4 NIF-IgGs detected) or its absence (44 patients, who mostly had ≤2 NIF-IgGs detected). Among NF-L-IgG positive patients, 19/21 had ≥1 subacute onset CNS disorders: cerebellar ataxia (11), ence...