Ab0157 High Prevalence of Biopsy-Proven Small Fiber Neuropathy in a Clinical Rheumatology Practice

Background: Small Fiber Neuropathy (SFN) is an increasingly recognized cause of widespread musculoskeletal and neuropathic pain. Other prominent symptoms associated with SFN include debilitating fatigue, stiffness, headaches, dry eyes, dry mouth, cognitive difficulty, abdominal pain, nausea, POTS like symptoms, sweating abnormalities, and sexual dysfunction. These are common symptoms exhibited by many rheumatology patients. Patients exhibiting these symptoms are often diagnosed with fibromyalgia. Studies show that up to 45% - 50% of fibromyalgia patients have a positive skin biopsy for SFN. A skin biopsy for SFN should be considered in all patients diagnosed with fibromyalgia. This procedure can be performed in the office and will aid in diagnosis and treatment of these complicated patients. Objectives: The objective of this review is to discern the utility of office based biopsies for small fiber neuropathy in diagnosis and treatment of clinic patients with widespread pain and related symptom complexes. Methods: This is a preliminary, observational, retrospective analysis of 59 patients in a private practice Rheumatology clinic suspected of having small fiber neuropathy. Patients with symptoms consistent with SFN underwent a punch biopsy of the skin to measure intraepidermal nerve fiber density. Two 3-mm punch biopsies were obtained, typically from the leg, one 10 cm proximal to the lateral malleolus and one 10 cm distal to the greater trochanter of hip. Results: Of the 59 skin biopsies obtained, 44 (73%) were positive, demonstrating decreased intraepidermal nerve fiber density. Fifteen (27%) were negative, indicating no decrease in intraepidermal nerve fiber density. 35 of the 44 patients (77%) positive for SFN had a current diagnosis of fibromyalgia. Conclusion: The high positivity rate in fibromyalgia suggests SFN may be a causative or contributing factor in widespread pain, fatigue, cognitive dysfunction, and autonomic dysfunction.The diagnosis of fibromyalgia presents challenges for both the patient and physician. Patients are often frustrated because they are told that nothing is seriously wrong in light of wholly normal diagnostic testing. In the United States, patients with fibromyalgia may not be accepted at certain referral centers because it is thought they will not respond to treatment. A positive biopsy for SFN may provide a different treatment approach for these patients. Patients with fibromyalgia and a positive skin biopsy may benefit from treatment for SFN. IVIG has been shown to have a beneficial effect in these patients. It is necessary to elucidate the true frequency of SFN in fibromyalgia and all autoimmune diseases. It is essential that the rheumatologist become familiar with this diagnosis and learn how to properly evaluate and treat this disease. REFERENCES: [1] Metyas S, Messiah R, Gettas T, Chen C, Arkfeld D. Small Fiber Neuropathy in Rheumatology Clinics [abstract]. Arthritis Rheumatol. 2016; 68 (suppl 10). https://acrabstracts.org/abstract/small-fiber-neuropathy-in-rheumatology-clinics/. Accessed January 14, 2024. Acknowledgements: NIL. Disclosure of Interests: None declared.