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An atypical case of SCN9A mutation presenting with global motor delay and a severe pain disorder



Introduction: Erythromelalgia due to heterozygous gain-of-function SCN9A mutations usually presents as a pure sensory–autonomic disorder characterized by recurrent episodes of burning pain and redness of the extremities. Methods: We describe a patient with an unusual phenotypic presentation of gross motor delay, childhood-onset erythromelalgia, extreme visceral pain episodes, hypesthesia, and self-mutilation. The investigation of the patient's motor delay included various biochemical analyses, a comparative genomic hybridization array (CGH), electromyogram (EMG), and muscle biopsy. Once erythromelalgia was suspected clinically, the SCN9A gene was sequenced. Results: The EMG, CGH, and biochemical tests were negative. The biopsy showed an axonal neuropathy and neurogenic atrophy. Sequencing of SCN9A revealed a heterozygous missense mutation in exon 7; p.I234T. Conclusions: This is a case of global motor delay and erythromelalgia associated with SCN9A. The motor delay may be attributed to the extreme pain episodes or to a developmental perturbation of proprioceptive inputs. Muscle Nerve 49: 134–138, 2014