High-dose flecainide for symptomatic relief in paramyotonia congenita/severe neonatal episodic laryngospasm due to SCN4A G1306E: a case report.

Abstract

Background: Severe neonatal episodic laryngospasm has been previously reported in multiple patients with the heterozygous pathogenic variant G1306E in SCN4A. Treatment can be difficult due to side effects from therapies utilized conventionally for the management of myotonia and paramyotonia congenita.

Case presentation: We report on two female siblings of Irish, Scandinavian, and German ethnicity aged 7 and 3 years with severe neonatal episodic laryngospasm and paramyotonia congenita due to a paternally inherited heterozygous pathogenic variant of the SCN4A gene and the use of high-dose flecainide therapy for symptomatic management. Interestingly, one of the two siblings has a coexisting separate maternally inherited and pathogenic CLCN1 variant that may further impact phenotype. High-dose flecainide 220-250 mg/m²/day was not associated with any cardiac side effects.

Conclusion: This report supports the use of high-dose flecainide in combination with standard therapies in pediatric patients with SCN4A mutations to modulate acute symptoms and provides suggested dosing with an acute and long-term monitoring protocol.