Erythromelalgia is a rare pain syndrome caused by gain-of-function mutations of the SCN9A gene. The gene encodes Na_v1.7 channels, preferentially located in the sympathetic ganglia and nociceptive sensory neurons of the dorsal root ganglia (DRG),¹ that play a key role in pain modulation.² DRG hyperexcitability leads to decreased pain threshold and increased firing frequency of pain signaling neurons.³ Clinically, this presents as recurrent, severe burning pain, redness, warmth, and often swelling of the distal extremities. Exposure to cold may provide relief but can lead to skin ulcerations.⁴ There is anecdotal evidence of partial relief from NSAIDS, antihistamines, and sodium channel blockers.^5,6 Carbamazepine and oxcarbazepine inactivate sodium channels but have been ineffective in most patients. Only 1 family with erythromelalgia and V400M mutation in the SCN9A gene that responded to carbamazepine was reported so far.³

红血脑痛是一种罕见的疼痛综合征，由SCN9A基因的功能获得性突变引起。该基因编码Na _v 1.7通道，优先位于背根神经节（DRG）¹的交感神经节和伤害感受性感觉神经元中，在痛觉调节中起关键作用。² DRG过度兴奋导致疼痛阈值降低，并且疼痛信号神经元的放电频率增加。^3在临床上，这表现为反复发作，剧烈的灼痛，发红，发热，并且经常导致远端肢体肿胀。暴露于寒冷可能会缓解疼痛，但会导致皮肤溃疡。⁴有轶事证据表明可以从NSAIDS，抗组胺药和钠通道阻滞剂中部分缓解。^5,6卡马西平和奥卡西平使钠通道失活，但对大多数患者无效。到目前为止，仅报道了一个对卡马西平有反应的SCN9A基因中有红斑性肌痛和V400M突变的家庭。³