Evidence of autoimmune etiology in children with small fiber neuropathy.

Objective: Small fiber neuropathy (SFN) is becoming increasingly recognized as a cause of autonomic dysfunction, sensory disturbances, and neuropathic pain. While SFN was previously considered predominantly idiopathic, cases of autoimmune SFN are now well described in adults but remain underexplored in children. Methods: In this retrospective chart review, we identified pediatric patients diagnosed with SFN of suspected autoimmune etiology. SFN was diagnosed based on epidermal nerve fiber density (ENFD) and/or sweat gland nerve fiber density (SGNFD) values from skin biopsy and/or quantitative sudomotor axon reflex testing (QSART). Autoantibodies were assessed using the Mayo Clinic Dysautonomia Panel and the Washington University in St. Louis (WUSTL) Sensory Neuropathy Panel. Results: Twenty patients with SFN of suspected autoimmune etiology were identified. Seventy-five percent were females, with mean ages at symptom onset and diagnosis of 11.158 and 14.038 years, respectively. Presenting symptoms included gastrointestinal (GI) symptoms (60%, Conclusion: Pediatric SFN typically presents with a combination of POTS, neurologic, and GI symptoms. Our study demonstrates a potential autoimmune etiology, supported by the presence of identifiable autoantibodies and observed clinical improvement after a minimum of 3 months of IVIG therapy.