Objective:

To report a case of small fiber neuropathy associated with an elevated GD1a antibody titer and treatment with intravenous immunoglobulin (IVIG)

Background:

Cryptogenic small fiber neuropathy (SFN) is a vexing clinical problem often with limited treatment options besides symptomatic control. Immune SFN typically presents with acute or subacute onset, non-length dependent pathology, female gender, and often association with various autoantibodies. A number of immune mechanisms have been proposed, but the role of autoantibodies is controversial. Previous studies have shown an association between SFN and TS-HDS, FGFR-3, Plexin D1, and other autoantibodies, and the role of these antibodies in identifying immunotherapy-responsive SFN is currently under investigation. Other reports have shown responsiveness to IVIG, steroids, or plasmapheresis in SFN related to sarcoidosis, Sjogren syndrome, vasculitis, and post-COVID SFN.

Design/Methods:

NA

Results:

A 58-year-old female reported a subacute onset of lower extremity pain, numbness and tingling. On examination the patient’s Utah Early Neuropathy Scale (UENS) score was 12/42. Patient-reported questionnaires revealed the following: SFN-Rasch Overall Disability Scale (SFN-RODS)=58/64, SFN-Symptom Inventory Questionnaire (SFN-SIQ)=11/39, SFN-Screening List (SFN-SL)=18/84 (>11 sensitive for SFN). EMG was normal, but sweat gland nerve fiber density was low in 2 sites, and QSART was abnormal in her distal leg. IgM-GD1a antibodies were present at a titer of 7000 (normal <2000); no other neuropathy cause was identified. After 6 months of IVIG treatment the UENS score was 1/42, SFN-RODS was 61/64, and SFN-SIQ was 13/39. The patient opted to discontinue IVIG treatment as symptoms had improved.

Conclusions:

This case of SFN with elevated GD1a autoantibody, and subjective and objective improvement on IVIG, highlights the importance of checking for autoantibodies in SFN. Anti- GD1a may be a useful biomarker in screening and managing patients with immune-mediated SFN and may be useful to predict response to immunotherapy, but further studies are needed.