Diagnosing Small Fiber Neuropathy in Sarcoidosis remains challenging

Abstract

Introduction Small fibre neuropathy (SFN) occurs in many sarcoidosis patients. A gold standard for diagnosing SFN is lacking but the diagnostic criteria using quantitative sensory testing (QST) and intra-epidermal nerve fiber density (IENFD) published by Devigili are being used in clinical practice. <b>Aims and objectives:</b> This study investigates whether the current diagnostic criteria are sufficient for diagnosing SFN specifically in patients with sarcoidosis. <b>Methods:</b> Clinical evaluation by a neurologist, the SFN screening list (SFNSL), nerve conduction studies, 10 um skin biopsy and quantitative sensory testing (QST) at both hands and feet are used to diagnose SFN. An intra-epidermal nerve fiber density (IENFD) &lt;40/mm2 is used as cut-off value for SFN. For abnormal QST, abnormal warm detection threshold (WDT) and cold detection threshold (CDT) on both feet with method of levels (LEV) and method of limits (LIM) is used and compared with the total amount of abnormal QST parameters. <b>Results:</b> Of 53 sarcoidosis patients with symptoms of sensory neuropathy only 8 patients were diagnosed with SFN based on the Divigili criteria. Remarkably, none of the patients had an abnormal QST. However, when we included the other QST parameters as well, we found a good correlation between the amount of abnormal parameters and clinical symptoms of SFN. <b>Conclusion:</b> Our data suggest that current diagnostic criteria for diagnosing Small Fiber Neuropathy may underestimate this diagnosis in patients with sarcoidosis. Using other abnormal parameters derived from the QST might improve the sensitivity of this test with regard to the diagnosis of SFN specifically in patients with sarcoidosis.