In the last three decades with the improvement of the diagnostic methods, it has become possible to evaluate the lesions of the small nerve fibers (types A-delta and C) in the skin. This condition is known as small-fiber neuropathy (SFN) and developing as a result of metabolic, genetic, toxic or immune-mediated factors, including sarcoidosis and several types of mycobacteriosis. Its main manifestations include sensory complaints, such as disorders of pain and temperature sensitivity and autonomic dysregulation of the cardiovascular, gastrointestinal, and urinary systems. The diagnosis of neuropathy of small fibers is established mainly on the patient’s clinical examination and anamnesis data, assessment of symptoms with validated neurological scales and performing a skin biopsy with measuring the density of intraepidermal nerve fibers. It is important to note that damage to fibers A delta and C types is not recorded during routine electroneuromyography, which makes diagnosis difficult. Treatment of this disease is a complex task, that including treatment of underlying disease, using painkillers, such as antidepressants and anticonvulsants of various groups, local anesthetics, such as lidocaine and capsaicin. Studies are being conducted on the effectiveness of intravenous immunoglobulins and antagonists of tumor necrosis factor alpha in the treatment of this pathology. This review presents information on the etiology, clinical and diagnostic aspects and the basics of therapy of SFN, which can improve the quality of medical care and quality of life of patients with sarcoidosis and tuberculosis. (For citation: Basantsova NY, Zinchenko YuS, Starshinova AA, Yablonskiy PK. Diagnostic evaluation of small-fiber neuropathies in various diseases (review). Pediatrician (St. Petersburg). 2018;9(6):101-110. doi: 10.17816/PED96101-110).