The small-fiber polyneuropathies (SFN) are a class of diseases in which the small thin myelinated (Aδ) and/or unmyelinated (C) fibers within peripheral nerves malfunction and can degenerate. SFN usually begins in the farthest, most-vulnerable axons, so distal neuropathic pain and symptoms from microvascular dysregulation are common. It is well known in adults, e.g. from diabetes, human immunodeficiency virus, or neurotoxins, but considered extremely rare in children, linked mostly with pathogenic genetic variants in voltage-gated sodium channels. However, increasing evidence suggests that pediatric SFN is not rare, and that dysimmunity is the most common cause. Because most pediatric neurologists are unfamiliar with SFN, we report the diagnosis and management of 5 Swiss children, aged 6-11y, who presented with severe paroxysmal burning pain in the hands and feet temporarily relieved by cooling-the erythromelalgia presentation. Medical evaluations revealed autoimmune diseases in 3 families and 3/5 had preceding or concomitant infections. The standard diagnostic test (PGP9.5-immunolabeled lower-leg skin biopsy) confirmed SFN diagnoses in 3/4, and autonomic function testing (AFT) was abnormal in 2/3. Blood testing for etiology was unrevealing, including genetic testing in 3. Paracetamol and ibuprofen were ineffective. Two children responded to gabapentin plus mexiletine, one to carbamazepine, two to mexiletine plus immunotherapy (methylprednisolone/IVIg). All recovered within 6 months, remaining well for years. These monophasic tempos and therapeutic responses are most consistent with acute post-infectious immune-mediated causality akin to Guillain-Barré large-fiber polyneuropathy. Skin biopsy and AFT for SFN, neuropathic-pain medications and immunotherapy should be considered for acute sporadic pediatric erythromelalgia.

中文翻译：

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五名被诊断为小纤维神经病的儿童的急性单相性红斑性肢痛症

小纤维多发性神经病 (SFN) 是一类疾病，其中周围神经内细小的有髓鞘 (Aδ) 和/或无髓鞘 (C) 纤维发生故障并可能退化。SFN 通常始于最远、最脆弱的轴突，因此远端神经性疼痛和微血管失调引起的症状很常见。它在成人中众所周知，例如糖尿病、人类免疫缺陷病毒或神经毒素，但在儿童中被认为极为罕见，主要与电压门控钠通道中的致病性遗传变异有关。然而，越来越多的证据表明，儿童 SFN 并不罕见，免疫异常是最常见的原因。由于大多数儿科神经科医生不熟悉 SFN，我们报告了 5 名年龄在 6-11 岁的瑞士儿童的诊断和治疗，表现为手脚剧烈阵发性烧灼痛，降温后暂时缓解——红斑性肢痛症。医学评估显示 3 个家庭有自身免疫性疾病，3/5 有先前或伴随的感染。标准诊断测试（PGP9.5 免疫标记小腿皮肤活检）确认 SFN 诊断为 3/4，自主神经功能测试 (AFT) 异常为 2/3。对病因学进行的血液检测未发现病因，包括 3 例中的基因检测。扑热息痛和布洛芬无效。两名儿童对加巴喷丁加美西律有反应，一名对卡马西平有反应，两名对美西律加免疫疗法（甲泼尼龙/IVIg）有反应。所有的人都在 6 个月内康复，并且多年来一直保持良好状态。这些单相节奏和治疗反应与急性感染后免疫介导的因果关系最一致，类似于格林巴利大纤维多发性神经病。SFN 的皮肤活检和 AFT、神经性疼痛药物和免疫治疗应考虑用于急性散发性小儿红斑性肢痛症。