Congenital Insensitivity to Pain and Anhydrosis: Diagnostic and Therapeutic Dilemmas revisited

Senso-immunology: the hidden relationship between sensory system and immune system

The primary sensory neurons involved in pain perception express various types of receptor-type ion channels at their nerve endings. These molecules are responsible for triggering neuronal excitation, translating environmental stimuli into pain signals. Recent studies have shown that acute nociception, induced by neuronal excitation, not only serves as a sensor for signaling life-threatening situations but also modulates our pathophysiological conditions. This modulation occurs through the release of neuropeptides by primary sensory neurons excited by nociceptive stimuli, which directly or indirectly affect peripheral systems, including immune function. Senso-immunology, an emerging research field, integrates interdisciplinary studies of pain and immunology and has garnered increasing attention in recent years. This review provides an overview of the systemic pathophysiological functions regulated by receptor-type ion channels, such as transient receptor potential (TRP) channels in primary sensory neurons, from the perspective of senso-immunology.

Senso-immunology: The Emerging Connection between Pain and Immunity

The sensory and immune systems have been studied independently for a long time, whereas the interaction between the two has received little attention. We have carried out research to understand the interaction between the sensory and immune systems and have found that inflammation and bone destruction caused by fungal infection are suppressed by nociceptors. Furthermore, we have elucidated the molecular mechanism whereby fungal receptors are expressed on nociceptors and skin epithelium, how they cooperate to generate fungal pain, and how colitis and bone metabolism are regulated by mechanosensors expressed on the gut epithelium. Recently, we found that nociceptors prevent septic death by inhibiting microglia via nociceptor-derived hormones. This review summarizes our current state of knowledge on pain biology and outlines the mechanisms whereby pain and immunity interact. Our findings indicate that the sensory and immune systems share a variety of molecules and interact with each other to regulate our pathological and homeostatic conditions. This prompted us to advocate the interdisciplinary science named "senso-immunology," and this emerging field is expected to generate new ideas in both physiology and immunology, leading to the development of novel drugs to treat pain and inflammation.

A Review of the Therapeutic Targeting of SCN9A and Nav1.7 for Pain Relief in Current Human Clinical Trials

Introduction

There is a great need to find alternative treatments for chronic pain which have become a healthcare problem. We discuss current therapeutic targeting Nav1.7.

Areas Covered

Nav1.7 is a sodium ion channel protein that is associated with several human pain genetic syndromes. It has been found that mutations associated with Nav1.7 lead to the loss of the ability to perceive pain in individuals that are otherwise normal. Several therapeutic interventions are presently undergoing preclinical and research using the methodology of damping Nav1.7 expressions as a methodology to decrease the sensation of pain leading to analgesia.

Expert Opinion

It is our strong belief that there is a viable future in the targeting of protein of Nav1.7 for the relief of chronic pain in humans. The review will look at the genomics associated with SCN1A and proteomic of Nav1.7 as a foundation to explain the mechanism of the therapeutic interventions targeting Nav1.7, the human disease that are associated with Nav1.7, and the current development of treatment for chronic pain whether in preclinical or clinical trials targeting Nav1.7 expressions. The development of therapeutic antagonists targeting Nav1.7 could be a viable alternative to the current treatments which have led to the opioid crisis. Therefore, Nav1.7 targeted treatment has a major clinical significance that will have positive consequences as it relates to chronic pain interventions.

Senso-immunology: crosstalk between nociceptive and immune systems

Understanding the molecular mechanisms of nociception has recently grown impressively. Nociception is mediated by mechanical, chemical, or microbial stimuli that evoke unpleasant feelings, alerting the host of the risk of tissue damage. Such diverse arrays of noxious stimuli trigger various escape reactions, usually altering immune homeostasis. Notably, nociceptors can recognize cytokines or pathogens via sensory molecules or innate immune receptors, participating in immune responses. Accumulating evidence suggests that activated nociceptors produce various humoral factors that affect the immune system and act like endocrine/paracrine signals. Thus, understanding the interplay between the nociceptive and immune systems may open new avenues for the development of an interdisciplinary research field, hereinafter referred to as 'senso-immunology'. This review will discuss the physiological relevance of the senso-immune system in the host defense context, focusing on how senso-immune research might yield novel treatments to cure pain and inflammation.

Loss of SLC9A6/NHE6 impairs nociception in a mouse model of Christianson syndrome

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Patients diagnosed with Christianson syndrome have intellectual disability, epilepsy, ataxia, and mutism, as well as hyposensitivity to pain. In this study, we use a mouse model of Christianson syndrome to demonstrate that this pain hyposensitivity is due in part to a decrease in excitability of nociceptors.

Children diagnosed with Christianson syndrome (CS), a rare X-linked neurodevelopmental disorder characterized by intellectual disability, epilepsy, ataxia, and mutism, also suffer from hyposensitivity to pain. This places them at risk of sustaining serious injuries that often go unattended. Christianson syndrome is caused by mutations in the alkali cation/proton exchanger SLC9A6/NHE6 that regulates recycling endosomal pH homeostasis and trafficking. Yet, it remains unclear how defects in this transporter lead to altered somatosensory functions. In this study, we validated a Nhe6 knockout (KO) mouse as a model of CS and used it to identify the cellular mechanisms underlying the elevated pain tolerance observed in CS patients. Within the central nervous system, NHE6 immunolabelling is detected in a small percentage of cortical neurons involved in pain processing, including those within the primary somatosensory and the anterior cingulate cortices as well as the periaqueductal gray. Interestingly, it is expressed in a larger percentage of nociceptors. Behaviourally, Nhe6 KO mice have decreased nocifensive responses to acute noxious thermal, mechanical, and chemical (ie, capsaicin) stimuli. The reduced capsaicin sensitivity in the KO mice correlates with a decreased expression of the transient receptor potential channel TRPV1 at the plasma membrane and capsaicin-induced Ca²⁺ influx in primary cultures of nociceptors. These data indicate that NHE6 is a significant determinant of nociceptor function and pain behaviours, vital sensory processes that are impaired in CS.

Case Study of a Rare Genetic Disorder: Congenital Insensitivity to Pain With Anhidrosis

A rare autosomal recessive disorder, congenital insensitivity to pain with anhidrosis, is characterised by the congenital lack of pain sensation. Other characteristic symptoms include no sweating, recurrent episodes of hyperpyrexia, retardation of mental abilities and self-mutilating behaviour. Herein, we present a case of a one-year-old male child who initially presented with self-bites on the tongue and then multiple fractures with no report of pain or crying, which initially indicated carelessness of parents. Based on further in-depth assessment indicating a family history of similar weak bones and no pain, the paediatric team conducted investigations along with genetic tests. The child was diagnosed with congenital insensitivity to pain with anhidrosis. Another sibling born later also had the same disorder. Both the children developed eczema, which was difficult to cure due to constant scratching by children as they did not feel any pain. Follow-up studies indicated a slight difficulty in learning abilities and delay in the achievement of milestones. This case report indicates the need for rigorous investigations in such cases to understand the aetiology and appropriate counselling of parents for the utmost care of the child.

Anesthetic management of children with congenital insensitivity to pain with anhidrosis

INTRODUCTION

Congenital analgesia is a rare autosomal recessive hereditary disease. The primary damage of congenital analgesia is central structure damage of comprehensive pain perception.

CASE PRESENTATION

A 1-year-old Han Chinese boy was admitted to hospital because of a tongue bite. He had no response to noxious stimulation of the body surface and was diagnosed with congenital analgesia. A small dose of remifentanil was intravenously injected during anesthetic induction to reduce the stress response caused by endotracheal intubation. A certain depth of anesthesia should be guaranteed during anesthetic induction and surgery to alleviate the stress response induced by endotracheal intubation and the operation.

CONCLUSION

Opioid analgesics are not required for general anesthesia in patient with congenital insensitivity to pain. With a heat dissipation barrier in patients with congenital insensitivity to pain with anhidrosis, body temperature, end-tidal carbon dioxide and bispectral index should be monitored.

Painless: a case of congenital insensitivity to pain in a 5-year-old male

Background: several genetic disorders are known to be associated with congenital insensitivity to pain (CIP), a term often used to describe an impaired ability to perceive the type, intensity and quality of noxious stimuli. Children with CIP often injure themselves severely. The injury can go unnoticed or be misdiagnosed as child abuse because it is associated with multiple and recurrent injuries which may result in permanent damage. Patient findings: we report the case of a 5-year-old boy with a history of showing no signs of pain when exposed to accidental injuries such as trauma, burns or secondary chronic lesions. Conclusion: child abuse has a much higher occurrence rate than rare neuropathies such as the one we describe. However, CIP should be considered as a diagnosis in any child presenting with a history of poor or absent responses to painful stimuli.

Office-Based Anesthetic and Oral Surgical Management of a Child With Hereditary Sensory Autonomic Neuropathy Type IV: A Case Report

Hereditary sensory and autonomic neuropathy type IV (HSAN IV), or congenital insensitivity to pain with anhidrosis, is an exceptionally rare genetic disorder that results in the complete loss of pain and temperature sensation as well as anhidrosis. Anesthetic management of these patients can be difficult because of significantly increased risks during general anesthesia. Literature on perioperative anesthetic management is typically written in the context of a hospital setting. As such, our case presents a unique report on the anesthetic management of a HSAN IV patient who presented for extraction of 2 teeth in an office-based setting. In determining how to safely manage the procedure, we decided against general anesthesia as we lacked the facilities and equipment to safely handle previously reported complications. We were successful in providing sedation with nitrous oxide in oxygen and applying 20% benzocaine topical ointment on the surgical site in lieu of administering general anesthesia. We had an anesthesiologist present and obtained intravenous access prior to the surgery to help manage any complications. This report provides support that simple dental extractions can be accomplished safely in the HSAN IV patient in the office-based setting, thereby avoiding unnecessary risk.

Oral manifestations, dental management, and a rare homozygous mutation of the PRDM12 gene in a boy with hereditary sensory and autonomic neuropathy type VIII: a case report and review of the literature

BACKGROUND

Hereditary sensory and autonomic neuropathy type VIII is a rare autosomal recessive inherited disorder. Chen et al. recently identified the causative gene and characterized biallelic mutations in the PR domain-containing protein 12 gene, which plays a role in the development of pain-sensing nerve cells. Our patient's family was included in Chen and colleagues' study. We performed a literature review of the PubMed library (January 1985 to December 2016) on hereditary sensory and autonomic neuropathy type I to VIII genetic disorders and their orofacial manifestations. This case report is the first to describe the oral manifestations, and their treatment, of the recently discovered hereditary sensory and autonomic neuropathy type VIII in the medical and dental literature.

CASE PRESENTATION

We report on the oral manifestations and dental management of an 8-month-old white boy with hereditary sensory and autonomic neuropathy-VIII over a period of 16 years. Our patient was homozygous for a mutation of PR domain-containing protein 12 gene and was characterized by insensitivity to pain and thermal stimuli, self-mutilation behavior, reduced sweat and tear production, absence of corneal reflexes, and multiple skin and bone infections. Oral manifestations included premature loss of teeth, associated with dental traumata and self-mutilation, severe soft tissue injuries, dental caries and submucosal abscesses, hypomineralization of primary teeth, and mandibular osteomyelitis.

CONCLUSIONS

The lack of scientific knowledge on hereditary sensory and autonomic neuropathy due to the rarity of the disease often results in a delay in diagnosis, which is of substantial importance for the prevention of many complications and symptoms. Interdisciplinary work of specialized medical and dental teams and development of a standardized treatment protocols are essential for the management of the disease. There are many knowledge gaps concerning the management of patients with hereditary sensory and autonomic neuropathy-VIII, therefore more research on an international basis is needed.

Congenital insensitivity to pain and anhydrosis due to a rare mutation and that is complicated by inflammatory bowel disease and amyloidosis: a case report

Patients with congenital insensitivity to pain and anhydrosis syndrome are at risk for renal amyloidosis and inflammatory bowel disease. Physicians caring for such patients should be aware of these complications.

Multidisciplinary assessment of congenital insensitivity to pain syndrome

BACKGROUND

Congenital insensitivity to pain and anhidrosis (CIPA) is a rare clinical condition characterized by the absence of normal subjective and objective responses to noxious stimuli in patients with intact central and peripheral nervous systems.

CASE PRESENTATIONS

Two patients with CIPA are reported. The first patient was a 13-year-old girl who presented to our hospital with multiple joint destructions secondary to osteomyelitis. The second patient was a 10-year-old boy who presented with multiple hand lesions and right leg osteomyelitis. Our patients were treated with multiple debridements and intravenous antibiotics according to our hospital protocol.

CONCLUSION

Early recognition of the disease is important. The treatment for this condition is focused more on the prevention of bone injuries and joint infection, as opposed to a cure. There are no standard techniques or guidelines available to treat this rare disease. Overall, effective CIPA treatment is built around family education and patient training.