Hôpital Necker-Enfants Malades

Mepyramine targets mutant Nav1.7 channels to relieve pain and erythema in primary erythromelalgia patients.

Gain-of-function mutations in , which encodes the Nav1.7 voltage-gated sodium channel, are known to cause primary erythromelalgia (PEM). This condition is characterized by recurrent episodes of erythema, burning pain, and warmth in the extremities. These genetic insights have spurred the development of Nav1.7 blockers as a promising therapeutic strategy for PEM. However, translating these findings into effective clinical treatments has remained challenging. In this study, we demonstrate that mepyramine, a compound previously shown to alleviate pain in animal models, effectively targets hNav1.7 channels carrying PEM-associated gain-of-function mutations, providing substantial pain relief in PEM patients. Using voltage-clamp recordings in human embryonic kidney (HEK) 293 cells, we demonstrated that mepyramine inhibits hNav1.7 channels carrying three distinct PEM mutations, I848T, L858F, and L1267V, which differentially affect the gating properties of hNav1.7. Importantly, mepyramine's efficacy was consistent regardless of how these mutations altered channel activation or inactivation properties. To evaluate its clinical potential, we administered a high-dose topical formulation of mepyramine to a group of PEM patients suffering from severe pain that was unresponsive to conventional analgesics, including cases with identified mutations. This treatment rapidly and durably reduced burning pain and erythema, providing meaningful relief for patients who had not responded to, or could not tolerate, previous therapies. These results suggest that mepyramine can inhibit PEM-associated Nav1.7 channel mutants and may offer a new therapeutic approach for PEM patients.

A cross-sectional study of erythromelalgia in patients with pachyonychia congenita.

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

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.

Reduction in pain following treatment with ranolazine in primary erythromelalgia: a case report.

Olmsted syndrome with erythromelalgia caused by recessive transient receptor potential vanilloid 3 mutations.

A new TRPV3 missense mutation in a patient with Olmsted syndrome and erythromelalgia.

Olmsted syndrome (OS) is a rare keratinizing disorder characterized by excessive epidermal thickening of the palms and soles, with clinical and genetic heterogeneity. Approximately 50 cases have been reported, with the molecular basis described in only 9. Recently, TRPV3 (transient receptor potential vanilloid 3) mutations were identified in autosomal-dominant OS in 7 sporadic cases and 1 familial case, whereas an MBTPS2 (membrane-bound transcription factor protease, site 2) mutation was reported in X-linked recessive OS. We report a new sporadic case of severe, atypical OS and its underlying genetic basis. Our patient is a young girl with severe nonmutilating (palmo)plantar keratoderma without periorificial keratotic plaques associated with intense acute flares of inflammation, itching, burning pain, vasodilatation, and redness of the extremities consistent with erythromelalgia. Whole exome sequencing of patient DNA identified a novel de novo heterozygous missense mutation within TRPV3, p.Leu673Phe, predicted to be damaging. This case study further implicates TRPV3 in OS pathogenesis. In addition, previous reports of OS have not described erythromelalgia as a clinical feature. Its occurrence in our patient could be a chance event, but, if associated with OS, the features of erythromelalgia may expand the phenotypic spectrum of this rare syndrome.

[When should a myeloproliferative syndrome be suggested in vascular medicine?].

Thrombotic events are frequent in polycythemia vera (PV) and in essential thrombocythemia (ET). The frequency of thrombotic complications at presentation of PV and ET is nearly 50%. The spectrum of thrombotic complications is broad: thrombosis of arteries, veins and microvessels have been reported. Venous thrombosis can involve all territories but PV and TE are the commonest underlying etiology for Budd-Chiari Syndrome and splanchnic veins thrombosis. Endogenous erythroid-colony formation may be seen in up to 78% of patients thought to have Budd Chiari Syndrome and in 48% of splanchnic veins thrombosis. Major arterial thrombotic complications occur in 20%, especially in the extremities and in cerebral circulation. Microcirculatory disturbances are common in ET, occurring in 29% at presentation and 27% during follow up. In the extremities, erythromelalgia, a characteristic syndrome of red and congested extremities with raised temperature and painful burning sensations, is noticed in 30 to 50% of TE. Other microcirculatory manifestations like acrocyanosis, blue toes, digital gangrene can occur. All of these manifestations are highly sensitive to aspirin. Cerebral microcirculatory symptoms occur in about one-third of patients: migraine, transient visual symptoms like scotomata, blurred vision are characterized by a sudden onset, a short duration and a sequential course. Three kinds of leg ulcers have been described: leg ulceration as a consequence of microcirculatory thrombosis, exceptionally, pyoderma gangrenosum, and leg ulcers attributed to side effects of hydroxyurea. Microcirculatory leg ulcers are the most common: they are painful, inflammatory and sometimes, necrotic. They heal with treatment of SMP. Hydroxyurea-induced leg ulcers are painful, fibrous and multiple in 60%. Cessation of hydroxyurea typically leads to wound healing. The Polycythemia Vera Study Group (PVSG) established diagnostic criteria for PV and TE. Because SMP can have incompletely expressed disease, other authors have proposed determination of serum erythropoietin, examination of bone marrow histology, and spontaneous endogenous colony assays for diagnosis of PV or TE. The individual thrombotic risk depends on elevated hematocrit for PV, age (> 60) and prior thrombosis for PV and TE. Congenital and acquired (antiphospholipid syndrome) thrombotic states probably increase the risk of thrombosis.

[Raynaud's phenomenon in children].

Raynaud's phenomenon has been described more than 140 years ago, its prevalence in the general population is high, and yet the underlying pathological mechanisms are only partly understood. In children, female preponderance has been reported, as it is also the case in adults, and the disease usually starts after the age of 10. Diagnosis and differential diagnosis, in particular with erythromelalgia, are usually made through patient's or parent's interrogatory. It is important to distinguish primary Raynaud's phenomenon, which is usually benign, from Raynaud's phenomenon secondary to connective tissue disease. To this regard, nailfold capillaroscopy is of great help, as may be more recently introduced techniques such as thermography and digital blood pressure response to cooling. Primary Raynaud's phenomenon usually only requires simple physical measures (avoidance of exposure to coldness, gloves in winter, ...) plus sometimes oral calcium blockers. By contrast, Raynaud's phenomenon secondary to connective tissue disease requires systemic investigations, assessment and treatment of the underlying disease and, in some cases, more aggressive treatments such as intravenous carboprostacyclin (Iloprost).