[Neuropathic pain as a symptom in autonomic neuropathies and other rare diseases : Small fiber neuropathy: its recognition, diagnosis, and treatment]. / Neuropathische Schmerzen als Symptom bei autonomen Neuropathien und anderen seltenen Erkrankungen : Kleinfaserneuropathie erkennen, diagnostizieren und behandeln.

BACKGROUND: Neuropathic pain is difficult to diagnose and treat. Small fiber neuropathy (SFN) flies under the radar of nerve conduction studies. OBJECTIVES: The importance of a structured patient history and physical examination in the context of neuropathic pain is emphasized. Describing SFN as an important cause, the authors consider rare but partially treatable differential diagnoses. They conclude that autonomic symptoms are frequently associated, often presenting with diverse symptoms. METHODS: A selective literature research to present SFN symptoms as well as differential diagnostic and therapeutic steps in the context of SFN and rare diseases focusing on the autonomic nervous system. RESULTS: Neuropathic pain significantly reduces quality of life. To shorten the time until diagnosis and to initiate therapy, the authors recommend a structured patient history including sensory plus and minus symptoms and non-specific autonomic signs. If the initial search for the cause is not successful, rare causes such as treatable transthyretin (ATTR) amyloidosis and Fabry's disease or autoimmune causes should be considered, particularly in the case of progressive and/or autonomic symptoms. CONCLUSION: The diagnosis and therapy of rare SFN requires interdisciplinary collaboration and, in many cases, a referral to specialized centers to achieve the best patient care.

Nonregional small fibre neuropathy in cases of autoimmune autonomic neuropathy.

OBJECTIVE: Autonomic small fibre neuropathy is described in patients with autoimmune autonomic neuropathy (AAN). Few data are available on somatosensory function and skin biopsies in AAN. METHODS: Retrospective analysis of 17 patients (51.2 ± 6.8 years, n = 7 males) with AAN, including autoantibodies, quantitative sensory testing (QST, n = 13) and intraepithelial nerve fibre density (IENFD) in skin biopsy (n = 16). QST was performed according to the DFNS protocol over hands and feet dorsum. QST data were compared to healthy controls. Comparison of antibody-positive and antibody-negative cases. RESULTS: 70.6% of patients were antibody positive. 82.4% described at least one episode with sensory symptoms. Skin biopsies revealed reduced IENFD in 58.8% of patients, whereas neuropathic pain was only present in 41.2%. QST showed a nonregional increase for nonpainful thermal and mechanical detection rather than for mechanical pain thresholds. Compared to healthy controls, sensory loss for cold and warm detection thresholds and for the thermal sensory limen-the temperature difference between alternating warm and cold stimuli-was found on hands and feet (all p < 0.05). For nonpainful mechanical stimuli, the vibration detection threshold on the hand was increased (p < 0.05). Of all pain thresholds, only the mechanical pain threshold was elevated for pinprick stimuli to the feet (p < 0.05). INTERPRETATION: Findings are consistent with a sensory small fibre more than large fibre neuropathy in AAN. Sensory loss was comparably distributed across hands and feet, indicating that nerve fibre dysfunction was rather generalized. Serostatus was not a significant predictor of the small fibre deficit present in AAN.