A comparison of different laboratory and clinical findings in Small fiber neuropathy (SFN) (P1.456)

Objective: This retrospective study aims to recognize distinctive clinical and paraclinical features of SFN in patients from Saint Louis University between 2014–2016. Background: SFN affects the axons of small, poorly myelinated (Aδ) and/or small, un-myelinated (C) fibers. Diagnosis is made primarily by the history and physical examination, but neurophysiologic testing and skin biopsy provides confirmation. Etiologies vary, with diabetes-mellitus being the most common. Previous studies have identified the association of immune-mediated SFN with trisulfated-disaccharide-IdoA2S-GlcNS-6S(TS-HDS) and Fibroblast Growth-Factor-Receptor(FGFR3) antigens. Design/Methods: The medical records were divided into categories of symptoms, signs, comorbidities and investigation findings. A key investigative tool used was the Washington University (WASH-U) Neuromuscular laboratory sensory panel which tests for antibodies against TS-HDS, FGF-R3, and MAG amongst others which have been associated with sensory predominant axonal neuropathies. Results: Mean age of the patients was 51±14.5 years. All patients were confirmed to have SFN by history, clinical exam and/or low intra-epidermal nerve fiber density(INFD). Large fiber involvement was ruled out via clinical exam and electrophysiologic tests. Of 117 patients, 55% tested positive for TS-HDS and 23% for FGFR3. 17.9% of the patients had DM, making the second cause of small fiber neuropathy in our cohort. 45% had low INFD on skin biopsies. 22% of patients had associated autonomic symptoms such as lightheadedness, dry mouth and eyes. Conclusions: SFN should be considered in all patients with painful neuropathy and normal electrodiagnostic study. In our patients, INFD was helpful in 45% of all cases. Looking for inflammatory/autoimmune markers like TSHDS and FGFR3 antibodies may be helpful in making final diagnosis as these markers were positive in 55% of our cases. Autonomic features are common in these patients. A larger sample is needed to conclude clinical manifestations of the symptoms, immune-mediated mechanism of the disease, antibody titers in association to the severity of INFD and responses to immune-modulating therapy. Disclosure: Dr. Massaquoi has nothing to disclose. Dr. Kafaie has nothing to disclose. Dr. Kumar has nothing to disclose. Dr. Chen has nothing to disclose. Dr. Naeem has nothing to disclose.