Key result
Protein-modifying mutations of NaV1.7 were found in only 14.6% (7 of 48) of patients with erythromelalgia, while the majority carried rare variants of uncertain causal significance.
Observational (n=48)
Functionally characterized mutations of NaV1.7 are present in only a minority of patients with erythromelalgia, though many carry rare variants of uncertain significance.
NaV1.7 mutations explain few EM cases; leaves open unidentified genetic drivers and targeted therapy potential.
Background and aim "Gain-of-function" mutations in voltage-gated sodium channel NaV1.7 have been linked to erythromelalgia (EM), characterized by painful hot and red hands and feet. We investigated the proportion of patients with EM that carry a mutation in NaV1.7 or in other pain-related genes and studied possible clinical differences. Methods In this study, 48 patients with EM were screened for mutations in a total of 29 candidate genes, including all sodium channel subunits, transient receptor potential channels (TRPA1, TRPV1, TRPM8), neurotrophic factors (NGF, NGFR, BDNF, GDNF, NTRK1 and WNK1) and other known pain-related genes (CACNG2, KCNS1, COMT, P2RX3, TAC1, TACR1), using a combination of next generation sequencing and classical Sanger sequencing. Results In 7/48 patients protein-modifying mutations of NaV1.7 (P187L, I228M, I848T (n = 4) and N1245S) were identified. Patients with the I848T mutation could be identified clinically based on early onset and severity of the disease. In contrast, there were no clinical characteristics that differentiated the other patients with NaV1.7 mutation from those patients without. We also found more than twenty rare protein-modifying genetic variants in the genes coding for sodium channels (NaV1.8, NaV1.9, NaV1.6, NaV1.5, NaV2.1, SCN1B, SCN3B), transient receptor potential channel (TRPA1, TRPV1), and other pain-related targets (WNK1 and NGFR). Conclusion We conclude that functionally characterized mutations of NaV1.7 (I848T) are present only in a minority of patient with EM. Albeit the majority of patients (27/48) carried rare protein-modifying mutations the vast majority of those will most probably not be causally linked to their disease. Implications The key question remaining to be solved is the possible role of rare variants of NaV1.8, NaV1.9, or beta-subunits in provoking chronic pain conditions or even EM.
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Zhang et al. (2014) conducted an observational in Erythromelalgia (n=48). Mutations in NaV1.7 and other pain-related genes was evaluated on Proportion of patients carrying a protein-modifying mutation in NaV1.7. Protein-modifying mutations of NaV1.7 were found in only 14.6% (7 of 48) of patients with erythromelalgia, while the majority carried rare variants of uncertain causal significance.
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