STUDY: Primary Erythermalgia as a Sodium Channelopathy: Scre

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Objectives  To elucidate the rate of missense mutations in the SCN9A gene (which encodes sodium channel Na_v1.7) (OMIM 603415) among patients with primary erythermalgia and to examine the possibility that other sodium channels can cause the disease.

Design  Case series.

Setting  Department of Medicine, Radboud University Nijmegen, the Netherlands.

Participants  Six patients with sporadic and 9 with unique familial primary erythermalgia.

Interventions  Questionnaire to determine clinical profile and sequencing of all coding exons from SCN9A and those of SCN10A (OMIM 604427) and SCN11A (OMIM 604385) in 2 selected cases with a clear family history of the disease.

Main Outcome Measures  Detection of SCN9A mutation.

Results  We identified 1 patient with an SCN9A mutation. This mutation (I848T) has been associated with primary erythermalgia. Sequencing of 2 other candidate genes did not show mutations in 2 patients with familial primary erythermalgia.

Conclusions  The Na_v1.7 voltage-gated sodium channels are related to syndromes of altered nociception. We detected a low SCN9A mutation rate in patients with primary erythermalgia, suggesting that pain syndromes in the skin may have a polygenic basis.

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