Université Paris-Saclay

To assess the contribution of large and small nerve fiber alteration in erythromelalgia (EM). Thirty-three EM patients were included and underwent clinical evaluation based on EM severity score, DN4, and Utah Early Neuropathy Scale (UENS) score. Neurophysiological evaluation consisted in nerve conduction studies (NCS) for large nerve fibers and specific tests for small nerve fibers: electrochemical skin conductance, cold and warm detection thresholds, and laser evoked potentials. Finally, the evaluation of vascular changes was based on the presence of clinical feature of microvascular disorders and the measurement of the Toe Pressure Index (TPI). While 28 patients (85%) had vascular alteration on TPI or clinical features, 23 patients (70%) had small-fiber neuropathy on neurophysiological tests, and only 10 patients (30%) had large fiber neuropathy on NCS. Regarding clinical scores, there was no difference between groups (presence or absence of large- or small-fiber neuropathy or microvascular disorder) except for a higher UENS score in patients with large fiber neuropathy. Peripheral neuropathy, mostly involving small nerve fibers, is almost as common as microvascular changes in EM, but remains inconstant and not related to a specific neuropathic pattern or higher clinical severity. The association of neuropathic and vascular factors is not systematic in EM, this syndrome being characterized by different pathophysiological mechanisms leading to a common clinical phenotype.

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Use of Epidermal Growth Factor Receptor Inhibitor Erlotinib to Treat Palmoplantar Keratoderma in Patients With Olmsted Syndrome Caused by TRPV3 Mutations.

Greco C, Leclerc-Mercier S, Chaumon S, Doz F, Hadj-Rabia S , et al.

JAMA dermatology • 2020-Feb-01

Olmsted syndrome is a genodermatosis characterized by painful and mutilating palmoplantar keratoderma (PPK) that progresses from infancy onward and lacks an effective treatment. It is most often caused by mutations in the transient receptor potential vanilloid 3 (TRPV3) gene. In animal models and keratinocyte cell lines, TRPV3 signaling leads to epidermal growth factor receptor (EGFR) transactivation. To examine the possibility of blocking EGFR transactivation with the inhibitor erlotinib hydrochloride to treat PPK in patients with Olmsted syndrome due to TRPV3 mutations. In this case series, 3 patients from 2 unrelated families who had TRPV3-mutation-associated PPK were treated with erlotinib from May 5, 2018, through May 13, 2019. Clinical follow-up included evaluation of PPK progression, pain and interventions for pain, as well as erlotinib dose adjustment based on treatment effect, plasma levels, and tolerance. The 3 patients (2 brothers aged 15 and 17 years and a 13-year-old girl) had severe palmoplantar hyperkeratosis, intolerable pain with erythromelalgia, severe growth delay, anorexia, and insomnia, which had been progressing since infancy despite numerous therapies. Two patients were confined to wheelchairs owing to intense pain and joint restrictions because of hyperkeratosis. All patients experienced depression and did not engage in social activities. Within 3 months of initiating therapy with erlotinib, hyperkeratosis and pain disappeared. All patients were able to touch the ground with their feet, wear shoes, and walk. Anorexia and insomnia remitted and paralleled improved growth. In addition, the patients resumed social activities. These improvements were sustained across 12 months of treatment and follow-up. The doses of erlotinib used were lower than those used in oncology, and only mild to moderate adverse effects were noted. The findings of this study report improvement of PPK in patients with Olmsted syndrome caused by TRPV3 mutations when treated with erlotinib. Targeting EGFR transactivation with erlotinib therapy may result in clinical remission in an orphan disease that lacks an effective intervention.

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