Primary Erythromelalgia in a 12-Year-Old Boy: Positive Response to Sodium Channel Blockers Despite Negative SCN9A Mutations

Abstract

Erythromelalgia is a rare disorder characterized by recurrent pain attacks, swelling and redness in the distal extremities. The primary forms of the disorder are caused by mutations in voltage-gated sodium channels. Treatment is difficult and controlled therapeutic studies offer little to no guidance. We report on a 12-year-old boy and his first occurrence of primary erythromelalgia. Genetic findings for mutations in the SCN9A gene, which encodes for the α-subunit of sodium channel Na_V1.7, were negative. Although initial treatment with sodium nitroprusside was ineffective, subsequent medication with lidocaine and mexiletine, in combination with gabapentin, was successful. Despite negative findings for mutations in the sodium channels, the use of sodium channel blockers should be considered in these patients.

Zusammenfassung

Die Erythromelalgie ist eine seltene Erkrankung, die durch wiederkehrende Schmerzattacken, Schwellungen und Rötungen der distalen Extremitäten charakterisiert ist. Die primären Formen sind durch Mutationen in den spannungs-abhängigen Natriumkanälen verursacht. Die Therapie ist schwierig und kontrollierte Therapiestudien fehlen. Wir berichten von einem 12-jährigen Jungen mit Erstmanifestation einer primären Erythromelalgie. Eine Mutationssuche im SCN9A-Gen, das für die α-Untereinheit des Natriumkanals Na_V1.7 kodiert, blieb negativ. Obwohl die initiale Therapie mit Natriumnitroprussid erfolglos blieb, zeigte die nachfolgende Therapie mit Lidocain und Mexiletin, in Kombination mit Gabapentin, einen guten klinischen Effekt. Trotz negativer Befunde für Mutationen in den Natriumkanälen sollte der Einsatz von Natriumkanalblockern bei Patienten mit primä­rer Erythromelalgie erwogen werden.

Key words

erythromelalgia - voltage-gated sodium channels - sodium nitroprusside - sodium channel blockers - lidocaine - mexiletine

Schlüsselwörter

Erythromelalgie - spannungsabhängige Natriumkanäle - Natriumnitroprussid - Natriumkanalblocker - Lidocain - Mexiletin

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