Tel Aviv University

Small-fiber neuropathy is rare in children. It has been associated with several autoimmune disorders, but there are no reports of an autoinflammatory etiology. The data of four children/adolescents presenting with erythromelalgia and neuropathic pain from 2014 to 2019 were collected retrospectively from the electronic database of a pediatric medical center. Results of clinical and/or electrophysiological evaluation excluded large nerve fiber involvement. Skin biopsy results confirmed small-fiber neuropathy. According to genetic analysis, two patients were heterozygous and one was homozygous for mutations in the familial Mediterranean fever (MEFV) gene. Behcet disease was diagnosed in the fourth patient. Treatment with anti-interleukin-1 agents, intravenous immunoglobulin, and glucocorticoids was beneficial. The diagnosis of small-fiber neuropathy should be considered in children/adolescents presenting with erythromelalgia. A thorough investigation is required to reveal the underlying disorder. Clinicians should be alert to the peripheral neurological manifestations of autoinflammatory syndromes because effective treatments are available.

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Chronic non-paroxysmal neuropathic pain - Novel phenotype of mutation in the sodium channel SCN9A gene.

Dabby R, Sadeh M, Gilad R, Lampl Y, Cohen S , et al.

Journal of the neurological sciences • 2011-Feb-15

Gain-of-function mutations in the SCN9A gene (encoding to NaV1.7 voltage-gated sodium channel) cause two rare paroxysmal pain disorders: inherited erythromelalgia (IEM) and paroxysmal extreme pain disorder (PEDP). These phenotypes are characterized by episodic extreme localized pain with cutaneous autonomic signs. So far, no other phenotypes have been associated with mutation in the SCN9A gene. To investigate mutations in the SCN9A gene in patients with chronic non-paroxysmal neuropathic pain. 9 patients with chronic severe unexplained neuropathic pain. Of the nine patients one had predicted pathologic mutations in the SCN9A gene. This patient had a heterozygous change of n.4648 T-C in exon 27 resulting in a substitution of W1550R, a highly conserved amino acid, predicting damage in the transmembrane S2 region, repeat IV. This mutation was not found in 50 controls. SCN9A mutations cause pain syndromes other than IEM and PEPD. These mutations should be considered in patients with resistant unexplained chronic neuropathic pain.

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