Open AccessPain triangle phenomenon in possible association with SCN9A : A case report
Author(s) -
Sopacua Maurice,
Hoeijmakers Janneke G. J.,
Kooi Anneke J.,
Merkies Ingemar S. J.,
Faber Catharina G.
Publication year - 2022
Publication title -
molecular genetics and genomic medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 29
ISSN - 2324-9269
DOI - 10.1002/mgg3.2026
Subject(s) - missense mutation , neuropathic pain , medicine , skin biopsy , sodium channel , chronic pain , biopsy , bioinformatics , dermatology , physical therapy , mutation , anesthesia , gene , genetics , biology , sodium , chemistry , organic chemistry
Abstract Background Voltage‐gated sodium channels are essential for the generation and conduction of electrical impulses in excitable cells. Sodium channel Na v 1.7, encoded by the SCN9A‐gene, has been of special interest in the last decades because missense gain‐of‐function mutations have been linked to a spectrum of neuropathic pain conditions, including inherited erythermalgia (IEM), paroxysmal extreme pain disorder (PEPD), and small fiber neuropathy (SFN). Methods In this case report, we present a 61‐year‐old woman who was referred to our tertiary referral center in a standard day care setting with suspicion of SFN. We performed additional investigations: skin biopsy to determine the intra‐epidermal nerve fiber density (IENFD), quantitative sensory testing (QST), and blood examination (including DNA analysis) for possible underlying conditions. Results The patient showed a clinical picture that fulfilled the criteria of IEM, PEPD, and SFN. DNA analysis revealed the heterozygous variant c.554G > A in the SCN9A‐gene (OMIM 603415). This variant has already been described in all three human pain conditions separately, but never in one patient having symptoms of all three conditions. Because its pathogenicity has never been functionally confirmed, the variant is classified as a variance of unknown significance (VUS)/risk factor. This suggests that another genetic and/or environmental substrate plays a role in the development of neuropathic conditions like described. Conclusion We have described this as the SCN9A ‐pain triangle phenomenon. Treatment should focus on pain management, genetic counseling, and improving/maintaining quality of life by treating symptoms and, if indicated, starting a rehabilitation program.