Corneal nerve quantification predicts the severity of symptoms in sarcoidosis patients with painful neuropathy

Small fiber neuropathy (SFN) is a debilitating condition characterized by chronic pain as well as sensory and autonomic dysfunction. SFN is an increasingly recognized component of a large number of diseases, including sarcoidosis. Although affecting an estimated 2-3% of the adult population in the United States, it often remains undiagnosed. Skin biopsy for evaluating intra-epidermal nerve fiber density (IENFD) and more recently corneal confocal microscopy (CCM) have been used to identify small fiber damage in patients with neuropathy. We demonstrate a significant reduction in IENFD, corneal nerve fiber number and length, with no change in the number of branches in patients with painful sarcoid neuropathy. Moreover, unlike IENFD, corneal nerve fiber number and length inversely correlate with the degree to which pain interferes with activities of daily living as assessed by the Brief Pain Inventory questionnaire. CCM thus constitutes an accurate, non-invasive assessment technique to aid in the diagnosis of SFN, as well as an objective marker of symptoms in patients with painful sarcoid neuropathy.