[Small fibre neuropathy: Diagnostic approach and therapeutic issues, and its association with primary Sjögren's syndrome]

Abstract

This article reviews the diagnostic issues and the therapeutic management of small fibre neuropathy (SFN), and a detailed literature analysis of its association with primary Sjögren's syndrome (pSS). A diagnosis of SFN should be raised in the presence of diffuse neuropathic painful manifestations (burning sensation, paresthesia, pricking, allodynia or hyperesthesia) and neurovegetative signs. The neurological examination and the electroneuromyogram are usually normal. The diagnosis of SFN can be confirmed by the evidence of decreased intra-epidermal nerve fibre density after a skin punch biopsy or the presence of abnormal nonconventional neurophysiological tests exploring the A-delta and C small nerve fibres (laser-evoked potentials, quantitative sensory tests, cutaneous sympathic reflex, autonomic function tests). The association of SFN and pSS has been scarcely evaluated, probably because of its lack of awareness and the low availability of the required diagnostic procedures. According to our literature review, pSS may be present in 9 to 30% of patients with SFN. Conversely, a pure SFN is present in 3 to 9% of patients with pSS where it may represent 25 to 35% of pSS-associated peripheral neuropathies. The treatment of SFN is mainly symptomatic and based on antalgic neuropsychotropic drugs and conventional analgesics. Corticosteroids and immunosuppressive drugs are usually unsuccessful. The effectiveness of intravenous immunoglobulins is only supported by a few case reports. SFN deserves to be separately evaluated among pSS-associated peripheral neuropathies. This requires a better availability of the appropriate diagnostic procedures, the investigation of underlying immunopathological mechanisms and the assessment of the new treatments recently proposed in pSS, mainly rituximab.