Small-Fiber Neuropathy

Small-fiber neuropathy (SFN) develops due to the impairment of fibers responsible for mediating temperature, pain, and autonomic functions. SFN complicates a number of common diseases such as diabetes mellitus, human immunodeficiency virus, and COVID-19, and is likely to be increasingly encountered. The associated pain contributes significantly to the morbidity of these diseases. Progression is slow, and most people affected by SFN do not develop large-fiber involvement over time. However, mixed polyneuropathies often start as SFN, and SFN often coexists with large fiber–predominant neuropathy. Symptoms of SFN, including painful paresthesia and dizziness, and sedative side effects of pain medications can negatively affect the quality of life. Standardized diagnostic criteria for SFN are not fully established, and skin biopsy remains the diagnostic test considered most reliable. Autonomic testing is useful when autonomic symptoms are present along with screening for associated conditions. Treatment should be individualized to control underlying causes and alleviate pain. Early diagnosis and individualized treatment are important for controlling SFN symptoms and optimizing daily functions. Here, we review the common but increasingly ignored condition, SFN, and discuss its diagnosis and management.