Experience with oral mexiletine in primary erythromelalgia in children

Erythromelalgia. Part II: Differential diagnoses and management

The management of erythromelalgia is challenging and requires multidisciplinary effort. Patient education is crucial as unsafe self-administered cooling techniques can lead to significant morbidity, including acral necrosis, infection, and amputation. The goal of management is pain control, reduction of flare frequency, and prevention of complications. This text is focused on the management of erythromelalgia and several other incompletely understood and under-recognized neurovascular disorders such as red scrotum syndrome, red ear syndrome, facial flushing, and complex regional pain syndrome.

Erythromelalgia: A Review of Medical Management Options and Our Approach to Management

Erythromelalgia (EM) is a rare disorder characterized by episodic, burning pain associated with erythema and warmth of the extremities. The feet and hands are most commonly affected. The pain can be so severe that patients may engage in behaviors, sometimes extreme, to cool the affected areas and change their lifestyle to avoid precipitating factors, such as exercise and increased ambient heat. A literature search was performed with PubMed and MEDLINE with the search term erythromelalgia. Inclusion criteria were studies on EM published after 1985 until January 1, 2022, in the English language and studies that provided information on medical treatment of EM. Studies were excluded if they were duplicates or did not include treatment data. No guidelines exist for the treatment of this complex disorder. Lifestyle modifications and pharmacologic treatments (topical and systemic) are discussed in this article, which provides a comprehensive review of published medical management options for erythromelalgia and a proposed approach to management.

Primary erythromelalgia mainly manifested by hypertensive crisis: A case report and literature review

BACKGROUND

Primary erythrocytic (PEM) is a rare autosomal dominant single gene disease. Most of the changes of gene loci can be found by whole exon gene sequencing, and the clinical symptoms and patient survival can be improved by specific site-to-site drug treatment. The other manifestations of this patient population are not remarkable. After the application of common drugs, the toxicity and side effects can be limiting. In addition to other common clinical manifestations, we found that the only unique manifestation of this patient was hypertensive crisis. Following multidisciplinary diagnosis and treatment (MDT), we decided to first control hypertension to alleviate the acute and critical patients. However, after controlling the hypertensive crisis, we unexpectedly found that the clinical symptoms of the patients had been significantly improved. Therefore, we concluded that the use of antihypertensive drugs can treat erythematous limb pain with the clinical manifestation of hypertensive crisis. Here, we describe a typical PEM disease, primary clinical features, diagnosis and treatment.

METHODS

Medical records of an 8-year-old boy with PEM were analyzed retrospectively, which included clinical characteristics, follow-up information, and SCN9A (Sodium Voltage-Gated Channel Alpha Subunit 9) gene analysis.

RESULTS

The 8-year-old boy had complained of abnormal paresthesia in his feet and ankles with burning sensation and pain for 2 years. The skin of both lower legs was red and underwent ichthyosis and lichenification. Genetic analysis confirmed the existence of a SCN9A gene mutation. The symptoms were gradually improved by treating with intravenous drip and oral administration of nitroglycerin to slow his heart rhythm.

CONCLUSION

Primary erythrocytic is characterized by skin ulceration, redness, elevated temperature, and severe burning pain primarily in both lower extremities. PEM can be diagnosed by genetic analysis. As this case demonstrates, treating with nitroglycerin as the drug of choice to control the hypertensive crisis significantly improved the symptoms of PEM and hypertension in this patient.

Acute monophasic erythromelalgia pain in five children diagnosed as small-fiber neuropathy

The small-fiber polyneuropathies (SFN) are a class of diseases in which the small thin myelinated (Aδ) and/or unmyelinated (C) fibers within peripheral nerves malfunction and can degenerate. SFN usually begins in the farthest, most-vulnerable axons, so distal neuropathic pain and symptoms from microvascular dysregulation are common. It is well known in adults, e.g. from diabetes, human immunodeficiency virus, or neurotoxins, but considered extremely rare in children, linked mostly with pathogenic genetic variants in voltage-gated sodium channels. However, increasing evidence suggests that pediatric SFN is not rare, and that dysimmunity is the most common cause. Because most pediatric neurologists are unfamiliar with SFN, we report the diagnosis and management of 5 Swiss children, aged 6-11y, who presented with severe paroxysmal burning pain in the hands and feet temporarily relieved by cooling-the erythromelalgia presentation. Medical evaluations revealed autoimmune diseases in 3 families and 3/5 had preceding or concomitant infections. The standard diagnostic test (PGP9.5-immunolabeled lower-leg skin biopsy) confirmed SFN diagnoses in 3/4, and autonomic function testing (AFT) was abnormal in 2/3. Blood testing for etiology was unrevealing, including genetic testing in 3. Paracetamol and ibuprofen were ineffective. Two children responded to gabapentin plus mexiletine, one to carbamazepine, two to mexiletine plus immunotherapy (methylprednisolone/IVIg). All recovered within 6 months, remaining well for years. These monophasic tempos and therapeutic responses are most consistent with acute post-infectious immune-mediated causality akin to Guillain-Barré large-fiber polyneuropathy. Skin biopsy and AFT for SFN, neuropathic-pain medications and immunotherapy should be considered for acute sporadic pediatric erythromelalgia.

Pediatric Erythromelalgia and SCN9A Mutations: Systematic Review and Single-Center Case Series

OBJECTIVES

To evaluate the clinical features of erythromelalgia in childhood associated with gain-of-function SCN9A mutations that increase activity of the Na_v1.7 voltage-gated sodium channel, we conducted a systematic review of pediatric presentations of erythromelalgia related to SCN9A mutations, and compared pediatric clinical presentations of symptomatic erythromelalgia, with or without SCN9A mutations.

STUDY DESIGN

PubMed, Embase, and PsycINFO Databases were searched for reports of inherited erythromelalgia in childhood. Clinical features, management, and genotype were extracted. Case notes of pediatric patients with erythromelalgia from the Great Ormond Street Hospital Pain Service were reviewed for clinical features, patient-reported outcomes, and treatments. Children aged over 10 years were recruited for quantitative sensory testing.

RESULTS

Twenty-eight publications described erythromelalgia associated with 15 different SCN9A gene variants in 25 children. Pain was severe and often refractory to multiple treatments, including nonspecific sodium channel blockers. Skin damage or other complications of cold immersion for symptomatic relief were common (60%). SCN9A mutations resulting in greater hyperpolarizing shifts in Na_v1.7 sodium channels correlated with symptom onset at younger ages (P = .016). Variability in reporting, and potential publication bias toward severe cases, limit any estimations of overall prevalence. In our case series, symptoms were similar but comorbidities were more common in children with SCN9A mutations. Quantitative sensory testing revealed marked dynamic warm allodynia.

CONCLUSIONS

Inherited erythromelalgia in children is associated with difficult-to-manage pain and significant morbidity. Standardized reporting of outcome and management in larger series will strengthen identification of genotype-phenotype relationships. More effective long-term therapies are a significant unmet clinical need.

Current pain management strategies for patients with erythromelalgia: a critical review

Erythromelalgia (EM) is a rare disorder characterized by erythematous, warm, painful extremities, which is often precipitated by cold conditions. The pathophysiology of EM is incompletely understood. Recent investigations have identified sodium channelopathy as a genetic cause for this pain condition, classified as primary inherited EM. Other subtypes are idiopathic EM and secondary EM. The management of pain in EM is challenging as no single therapy has been found to be effective. There is varying response to pharmacotherapy and significant variability within this clinical population, resulting in a stepwise trial and error approach. Consequently, EM is often associated with poorer health-related quality of life with higher morbidity. There is currently no consensus or guidelines on management of pain in EM. This is a review of the literature on management of pain using pharmacologic, procedural intervention and nonpharmacologic treatment in children and adults with EM.

Primary erythromelalgia: a review

Primary erythromelalgia (PE ORPHA90026) is a rare autosomal dominant neuropathy characterized by the combination of recurrent burning pain, warmth and redness of the extremities. The incidence rate of PE ranges from 0.36 to 1.1 per 100,000 persons. Gender ratio differs according to different studies and no evidence showed a gender preference. Clinical onset of PE is often in the first decade of life. Burning pain is the most predominant symptom and is usually caused and precipitated by warmth and physical activities. Reported cases of PE contain both inherited and sporadic forms. Genetic etiology of PE is mutations on SCN9A, the encoding gene of a voltage-gated sodium channel subtype Nav1.7. Diagnosis of PE is made upon clinical manifestations and screening for mutations on SCN9A. Exclusion of several other treatable diseases/secondary erythromelalgia is also necessary because of the lack of biomarkers specifically for PE. Differential diagnoses can include Fabry disease, cellulites, Raynaud phenomenon, vasculitis and so on. Diagnostic methods often involve complete blood count, imaging studies and thermograph. Treatment for PE is unsatisfactory and highly individualized. Frequently used pain relieving drugs involve sodium channel blockers such as lidocaine, carbamazepine and mexiletine. Novel drugs such as PF-05089771 and TV-45070 could be promising in ameliorating pain symptoms due to their Nav1.7 selectivity. Patients’ symptoms often worsen over time and many patients develop ulcerations and gangrenes caused by excessive exposure to low temperature in order to relieve pain. This review mainly focuses on PE and the causative gene SCN9A -- its mutations and their effects on Nav1.7 channels’ electrophysiological properties. We propose a genotype-channelopathy-phenotype correlation network underlying PE etiology which could provide guidance for future therapeutics.

An Egyptian child with erythromelalgia responding to a new line of treatment: a case report and review of the literature

Introduction

Erythromelalgia is a rare clinical syndrome characterized by episodic erythema, warmth and intense burning pain, which commonly involves the extremities. For those affected, this disorder may lead to significant long-term morbidity. Unfortunately, to date, no definitive therapy is available. This case report describes an Egyptian child with primary erythromelalgia that manifested at an early age and showed partial response to therapy with cetirizine hydrochloride. This anecdotal case report may have a diagnostic value for clinicians who have not seen this disorder.

Case presentation

A 34-month-old previously healthy right-handed Hamitic boy without any significant past medical history presented at the age of 2 years with episodic bilateral pain in his feet. His mother reported associated warmth and erythema localized to his feet that never extended beyond his ankle joints. This pain is triggered by exertion and/or warm temperature exposure and is relieved by cooling measures. The diagnosis of erythromelalgia was made based on the patient’s medical history and a thorough physical examination during the episodes. No evidence of local or systemic infection was present. Other causes for the symptoms were excluded by a negative extensive diagnostic work-up. Our patient did not respond to ibuprofen (15mg/kg/dose) three times a day but partial improvement with the oral non-sedating antihistaminic cetirizine hydrochloride (2.5mg/kg/once daily) was observed. When the child stopped cetirizine hydrochloride for 1 month as a test, the symptoms became aggravated and were relieved when cetirizine therapy was restarted. Cetirizine hydrochloride had not previously been reported to have this effect in children with erythromelalgia.

Conclusions

Erythromelalgia is a clinical syndrome of which the etiology, diagnosis and management are controversial. We describe a case of a 34-month-old Egyptian child with primary erythromelalgia that manifested at an early age. We believe that this is the first Egyptian case report of this kind in the literature. Partial response of this patient to cetirizine hydrochloride may grant us a new clue to understanding this mysterious condition.

Neuropathic pain in children

Neuropathic pain (NP), due to a lesion or disease of the somatosensory nervous system, is not well documented or researched in children. NP is a clinical diagnosis that can be difficult, especially in younger children. Nevertheless, it is important to recognise NP, as pain mechanisms and consequently management and prognosis differ from other types of long-term pain. NP is common in adult pain clinics but many of the underlying disease states in which it occurs are infrequently or never encountered in paediatric practice. However, NP in childhood has been reported, even in the very young in certain clinical situations. Causes of NP include traumatic injury, complex regional pain syndrome type II, cancer and chemotherapy, chronic infection, neurological and metabolic disease, and inherited sensory nerve dysfunction. The clinical and laboratory study of traumatic peripheral nerve injury has revealed important age-related differences in clinical presentation and prognosis. It is clear that mechanisms operating during development can profoundly modify the consequences of nerve damage and NP. Clinically, diagnosis, assessment and treatment of NP are based on methods and evidence derived from data in adults. Improvements in the understanding and management of NP are likely to come from developmentally appropriate improvements in the clarity and consistency of diagnosis and systematic, well-researched approaches to treatment.

Neurological perspectives on voltage-gated sodium channels

The activity of voltage-gated sodium channels has long been linked to disorders of neuronal excitability such as epilepsy and chronic pain. Recent genetic studies have now expanded the role of sodium channels in health and disease, to include autism, migraine, multiple sclerosis, cancer as well as muscle and immune system disorders. Transgenic mouse models have proved useful in understanding the physiological role of individual sodium channels, and there has been significant progress in the development of subtype selective inhibitors of sodium channels. This review will outline the functions and roles of specific sodium channels in electrical signalling and disease, focusing on neurological aspects. We also discuss recent advances in the development of selective sodium channel inhibitors.

Erythromelalgia: An Uncommon Presentation Precipitated by Aspirin Withdrawal

Erythromelalgia is a rare disorder frequently associated with myeloproliferative disorders. We describe a case of elderly patient diagnosed with myeloproliferative disorder in remission. The patient was on aspirin for secondary prevention of stroke and was taken off aspirin and developed erythromelalgia within two weeks of withdrawal of aspirin. After restarting aspirin, patient's symptoms improved within 2 weeks.

Refractory erythromelalgia of the ears: response to mexiletine

Erythromelalgia is a rare condition characterized by burning pain, erythema, swelling, and increased temperature usually in the extremities. We present an unusual presentation of erythromelalgia of the ears in a patient who has been refractory to multiple therapies and in whom relief of symptoms was achieved with the use of mexiletine. A review of clinical presentation, pathophysiology, and therapeutic options are presented.

Sodium channelopathies and pain

Chronic pain often represents a severe, debilitating condition. Up to 10% of the worldwide population are affected, and many patients are poorly responsive to current treatment strategies. Nociceptors detect noxious conditions to produce the sensation of pain, and this signal is conveyed to the CNS by means of action potentials. The fast upstroke of action potentials is mediated by voltage-gated sodium channels, of which nine pore-forming alpha-subunits (Nav1.1-1.9) have been identified. Heterogeneous functional properties and distinct expression patterns denote specialized functions of each subunit. The Nav1.7 and Nav1.8 subunits have emerged as key molecules involved in peripheral pain processing and in the development of an increased pain sensitivity associated with inflammation and tissue injury. Several mutations in the SCN9A gene encoding for Nav1.7 have been identified as important cellular substrates for different heritable pain syndromes. This review aims to cover recent progress on our understanding of how biophysical properties of mutant Nav1.7 translate into an aberrant electrogenesis of nociceptors. We also recapitulate the role of Nav1.8 for peripheral pain processing and of additional sodium channelopathies which have been linked to disorders with pain as a significant component.