Erythromelalgia: Small-Fiber Neuropathy by Any Other Name?

Abstract

In Reply.I thank Dr Oaklander for her informative letter and comments. I share her view that symptom-based diagnostic names are often imprecise and the use of diagnostic names that describe an underlying pathophysiologic mechanism are preferred. Certainly, as stated in our case report and her letter, there is mounting evidence that some, if not all, patients with primary erythromelalgia have mutations involving the Nav1.7 sodium channel located on chromosome 2q.1–3 Yet, those responsible for elucidating this defect refer to the disease as erythermalgia or erythromelalgia in recent reports, and they have not suggested a new name for the condition.1–3 It would be presumptive of me to rename erythromelalgia based on my clinical experience with this patient.When I first saw this patient, he had a 9-year history of bilateral episodic burning foot pain associated with redness and warmth in the painful regions. The pain was brought on by heat and activity and relieved by rest and cooling. Other than the physical findings of reddened, warm, and thickened skin primarily of his feet and to a lesser extent in his hands, this patient's general physical examination on presentation and now is entirely normal. Neurologic examination reveals no deficits in sensory or motor function, normal deep-tendon reflexes, and the absence of allodynia. Many of the conditions suggested by Dr Oaklander were ruled out by his history, physical examination, and laboratory investigations as outlined in the report, which were entirely normal. One notable exception was Fabry's disease, and thus we ran the appropriate tests. However, our evaluation of this patient continues today. Before receiving Dr Oaklander's letter, the patient and parents consented to undergo genomic DNA analysis to determine if he possesses the “primary erythermalgia-susceptibility gene.”3 I am awaiting these results. I am also now planning, at Dr Oaklander's suggestion, to obtain quantitation of nerve endings in PGP9.5-immunolabeled skin biopsies. This test is not currently available at my institution, however, and the family has not given consent to undergo the test at this time.Our intention in publishing this brief report was to bring attention to the fact that continuous intravenous lidocaine infusion and oral mexiletine may be useful in some adolescent patients with erythromelalgia who do not respond to aspirin, anticonvulsants, tricyclic antidepressants, sodium nitroprusside, or epidural anesthesia. An added benefit to me and other readers has been to spur the interest of Dr Oaklander.