An Atypical Case of an SCN9A Mutation with Global Motor Delay and Erythromelalgia (IN1-1.010)

OBJECTIVE: To describe the atypical clinical presentation of a patient with an SCN9A mutation. BACKGROUND: Erythromelalgia is characterized by recurrent episodes of burning pain and redness of the extremities and is caused by heterozygote gain-of-function mutations in the SCN9A gene, coding for the NAv1.7 channel. It usually presents as a pure sensory-autonomic disorder. We describe a patient with an SCN9A mutation and an usual phenotypic presentation of gross motor delay, childhood-onset erythromelalgia, extreme visceral pain episodes, followed by hypoesthesia and automutilation. DESIGN/METHODS: The investigation of the patient9s motor delay included various biochemical analyses, an EMG, a muscle biopsy, and a quantitative PCR of SMN1 . Once erythromelalgia was suspected, the SCN9A gene was sequenced. Sequential therapeutic trials of amitriptyline, gabapentin, carbamazepine and mexiletine were attempted. RESULTS: The EMG, CGH, EEG and metabolic tests were negative. The sural nerve biopsy showed an axonal neuropathy, whereas the muscle biopsy showed signs of neurogenic atrophy. Sequencing of the SCN9A gene revealed a heterozygote missense mutation in exon 7; p.I234T. CONCLUSIONS: We present the first case of global motor delay and erythromelalgia associated with an SCN9A mutation. The gross motor delay might be attributed to the extreme pain episodes or to a developmental perturbation of sensory-motor integration. Disclosure: Dr. Meijer has nothing to disclose. Dr. Vanasse has received personal compensation for activities with Janssen as a speaker. Dr. Vanasse has received research support from L9Institut de recherche Yves Ponroy. Dr. Nizard has nothing to disclose. Dr. Robitaille has nothing to disclose. Dr. Rossignol has nothing to disclose.