Homozygosity for a Rare Plec Variant Suggests a Contributory Role in Congenital Insensitivity to Pain.

Congenital insensitivity to pain is a rare human condition in which affected individuals do not experience pain throughout their lives. This study aimed to identify the molecular etiology of congenital insensitivity to pain in two Thai patients. Clinical, radiographic, histopathologic, immunohistochemical, and molecular studies were performed. Patients were found to have congenital insensitivity to pain, self-mutilation, acro-osteolysis, cornea scars, reduced temperature sensation, tooth agenesis, root maldevelopment, and underdeveloped maxilla and mandible. The skin biopsies revealed fewer axons, decreased vimentin expression, and absent neurofilament expression, indicating lack of dermal nerves. Whole exome and Sanger sequencing identified a rare homozygous variant c.4039C>T; p.Arg1347Cys in the plakin domain of Plec, a cytolinker protein. This p.Arg1347Cys variant is in the spectrin repeat 9 region of the plakin domain, a region not previously found to harbor pathogenic missense variants in other plectinopathies. The substitution with a cysteine is expected to decrease the stability of the spectrin repeat 9 unit of the plakin domain. Whole mount in situ hybridization and an immunohistochemical study suggested that Plec is important for the development of maxilla and mandible, cornea, and distal phalanges. Additionally, the presence of dental anomalies in these patients further supports the potential involvement of Plec in tooth development. This is the first report showing the association between the Plec variant and congenital insensitivity to pain in humans.

Phenotypes of a toddler with hereditary sensory and autonomic neuropathy type IV: comparing with normal: A case report.

RATIONALE: Hereditary sensory and autonomic neuropathy type IV (HSAN IV) may be misdiagnosed because of low awareness among clinical professionals and overlap with other subtypes of congenital insensitivity to pain (CIP). PATIENT: The patient was a 1-year-and-5-months-old boy whose main symptoms were delayed psychomotor development and recurrent fever. Whole-exome sequencing (WES) revealed a compound heterozygous mutation (c. 1927C > T, c. 851-33T > A) in the NTRK1 gene of the child. Pathological analysis showed decreased autonomic small nerve fibers, sparse hair follicles, and atrophy of the sweat glands. Sweat glands lack innervating nerve fibers. Brain magnetic resonance imaging (MRI) of the patient showed delayed myelination in the brain, slightly enlarged bilateral lateral ventricles, and patchy abnormal signals in the brain. DIAGNOSIS: hereditary sensory and autonomic neuropathy type IV (HSAN IV). INTERVENTION: Inform parents about the illness and take good care of the child. OUTCOMES: The children had less self-harming behavior and no painless fractures during follow-up at 2 years. LESSONS: This report describes the pathological and imaging features and clinical manifestations of a child with HSAN IV in early life to provide a reference for the early diagnosis of the disease. Early diagnosis can help avoid self-mutilation and painless injury and reduce wound infection.

A novel mutation in the SCN9A gene associated with congenital insensitivity to pain, anhidrosis, and mild cognitive impairment.

Congenital insensitivity to pain (CIP) is a rare phenotype characterized by the inability to perceive pain stimuli with subsequent self-injuries, whereas CIP associated with anhidrosis (CIPA) is an overlapping phenotype mainly characterized by insensitivity to noxious stimuli and anhidrosis. CIP is primarily associated with pathogenetic variants in the SCN9A gene while CIPA is associated with pathogenetic variants in NGF and NRTK genes. However, in recent years, a significant overlap between these two disorders has been observed highlighting the presence of anhidrosis in SCN9A variants. We report the cases of two siblings (age 4 and 6 years) born from consanguineous parents presenting with a previously undescribed phenotype due to a novel pathogenic variant in SCN9A clinically characterized by congenital insensitivity to pain, anhidrosis, and mild cognitive impairment.

Genetic landscape of congenital insensitivity to pain and hereditary sensory and autonomic neuropathies.

Congenital insensitivity to pain (CIP) and hereditary sensory and autonomic neuropathies (HSAN) are clinically and genetically heterogeneous disorders exclusively or predominantly affecting the sensory and autonomic neurons. Due to the rarity of the diseases and findings based mainly on single case reports or small case series, knowledge about these disorders is limited. Here, we describe the molecular workup of a large international cohort of CIP/HSAN patients including patients from normally under-represented countries. We identify 80 previously unreported pathogenic or likely pathogenic variants in a total of 73 families in the >20 known CIP/HSAN-associated genes. The data expand the spectrum of disease-relevant alterations in CIP/HSAN, including novel variants in previously rarely recognized entities such as ATL3-, FLVCR1- and NGF-associated neuropathies and previously under-recognized mutation types such as larger deletions. In silico predictions, heterologous expression studies, segregation analyses and metabolic tests helped to overcome limitations of current variant classification schemes that often fail to categorize a variant as disease-related or benign. The study sheds light on the genetic causes and disease-relevant changes within individual genes in CIP/HSAN. This is becoming increasingly important with emerging clinical trials investigating subtype or gene-specific treatment strategies.

Identification of founder and novel mutations that cause congenital insensitivity to pain (CIP) in palestinian patients.

BACKGROUND: Congenital insensitivity to pain (CIP) is a rare autosomal recessive disorder characterized primarily by an inability to perceive physical pain from birth, resulting in the accumulation of bruising, inflammation, and fractures that affect patient's life expectancy. CIP has different forms including CIP and CIPA. CIP with Anhidrosis (CIPA) is the most common type of CIP, which is caused mainly by mutations in NTRK1 and NGF genes, and is characterized by mental retardation and the inability to sweat (Anhidrosis). Because of high consanguinity rates in Palestine, this rare disease appears to have a higher frequency than in other communities. However, there were no systematic studies to address the genetic factors that cause CIP in the Palestinian community. METHODS: In our study, we used Sanger and Whole exome sequencing to genotype members of five CIP-affected Palestinian families. RESULTS: Our results confirm the presence of the founder c.1860-1861insT mutation in the NTRK1 gene of Palestinian Bedouin CIPA patients. Furthermore, one CIPA family carried a missense c.2170 G > A (G724 S) mutation in exon 16 of the NTRK1 gene. Finally, a novel nonsense c.901 A > T mutation (K301*) was detected in exon 7 of the SCN9A gene in CIP without anhidrosis family. CONCLUSIONS: Our study revealed three mutations that cause CIP and CIPA in the Palestinian community, which can help in improving the process of diagnosis and genetic counseling and establishing protocols for the diagnosis and follow-up for the affected individuals. This is especially important given that early diagnosis and medical care interference can prevent unpleasant CIP and CIPA complications.

Novel SCN9A variant associated with congenital insensitivity to pain.

BACKGROUND: Congenital insensitivity to pain (CIP) is a rare autosomal recessive syndrome characterized by lack of pain perception and a wide spectrum of clinical signs such as anosmia and hyposmia. Variants in SCN9A gene are associated with CIP. We here report on a Lebanese family with three CIP patients referred for genetic investigations. METHODS AND RESULTS: Whole exome sequencing analysis revealed the presence of a novel nonsense, homozygous SCN9A pathogenic variant: SCN9A (NM_001365536.1): c.4633G > T, p.(Glu1545*) in exon 26. CONCLUSION: Our three Lebanese patients had CIP, urinary incontinence and normal olfactory function while two of them also presented with osteoporosis and osteoarthritis; this association of features has not been previously reported in the literature. We hope that this report would contribute to a better delineation of the phenotypic spectrum associated with SCN9A pathogenic variants.

SCN9A variant in a family of mixed breed dogs with congenital insensitivity to pain.

BACKGROUND: Congenital insensitivity to pain (CIP) and hereditary sensory and autonomic neuropathies (HSANs) are a rare group of genetic disorders causing inability to feel pain. Three different associated variants have been identified in dogs: 1 in Border Collies, 1 in mixed breed dogs, and 1 in Spaniels and Pointers. OBJECTIVES: To clinically and genetically characterize CIP in a family of mixed breed dogs. ANIMALS: Two mixed breed dogs from the same litter were independently presented: 1 for evaluation of painless fractures, and the other for chronic thermal skin injuries. METHODS: Physical, neurological, and histopathological evaluations were performed. Whole genome sequencing of 1 affected dog was used to identify homozygous protein-changing variants that were not present in 926 control genomes from diverse dog breeds. RESULTS: Physical and neurological examinations showed the absence of superficial and deep pain perception in the entire body. Histopathological evaluations of the brain, spinal cord and sensory ganglia were normal. Whole genome sequencing identified a homozygous missense variant in SCN9A, XM_038584713.1:c.2761C>T or XP_038440641.1:(p.Arg921Cys). Both affected dogs were homozygous for the mutant allele, which was not detected in 926 dogs of different breeds. CONCLUSIONS AND CLINICAL IMPORTANCE: We confirmed the diagnosis of CIP in a family of mixed breed dogs and identified a likely pathogenic variant in the SCN9A gene. The clinical signs observed in these dogs mimic those reported in humans with pathogenic SCN9A variants causing CIP. This report is the first of a spontaneous pathogenic SCN9A variant in domestic animals.

Ocular manifestations among patients with congenital insensitivity to pain due to variants in PRDM12 and SCN9A genes.

Congenital insensitivity to pain (CIP) is a group of rare genetic disorders with a common characteristic of absent sensation to nociceptive pain. Here we present a series of six patients; three had a novel variant in the PRDM12 gene (group A), and three had a missense variant in the SCN9A gene (group B). We compared the ocular manifestations between the two groups. Records of these patients from 2009 through 2018 were reviewed. The retrieved data included demographics, genetic analysis results, ocular history and ophthalmic findings including visual acuity, corneal sensitivity, tear production, ocular surface findings, cycloplegic refraction, and fundoscopy. We found that patients with PRDM12 variant had more severe manifestations of ocular surface disease, with more prevalent corneal opacities and worse visual acuity, compared to patients with SCN9A variant.

[Marsili syndrome manifested by fever: a case report and literature review].

Objective: To describe the clinical features, genetic characteristics, and diagnosis of Marsili syndrome, an extremely rare disease which should be differentiated from other fever disorders. Methods: The clinical data and diagnostic process of a case with Marsili syndrome, hospitalized in the Department of Respiratory and Critical Care Medicine, the Eighth Medical Center of Chinese PLA General Hospital in February 2021, were summarized. The exon regions of 20, 000 genes of peripheral blood were detected in the patient and her parents. Using key words of"Marsili syndrome"and"ZFHX2 gene mutation", the related literatures were searched in Wanfang and PubMed databases from January, 2000 to November, 2021. In addition, the literatures of congenital insensitivity to pain and anhidrosis were retrieved in Wanfang domestic database from the same period. Results: A 23-year-old female patient had suffered from recurrent fever for more than two years, accompanied by anhidrosis, insensitive to pain and weakened corneal reflex. The effect of non-steroidal anti-inflammatory drugs for fever was minimal. The ZFHX2 gene mutation was positive in the patient and her mother, while NTRK1 gene mutation specific to congenital insensitivity to pain with anhidrosis (CIPA) was negative. The ZFHX2 gene mutation was negative in her father. A total of 2 literatures of Marsili syndrome were retrieved and a total of 6 cases of Marsili syndrome in one family were reported worldwide up to now. These patients had a group of similar symptoms including fever, little or no sweating, and insensitivity to pain caused by skin burn and bone fracture. However, there was no abnormality in headache and visceral pain, and female patients' childbirth pain as well as tactile sensation in these cases. The corneal reflex was decreased or negative. They had less sensitivity to stimulus of capsaicin. The ZFHX2 gene mutation was positive, but NTRK1 gene was not detected in all patients. A total of 4 literatures were retrieved and a total of 34 cases of CIPA were reported in China. Though Marsili syndrome and CIPA exhibited a number of similar clinical manifestations, they were distinct diseases and had obviously different outcome. Conclusions: Marsili syndrome is an autosomal dominant genetic disease. It is extremely rare worldwide. In clinical practice, when a patient presents with unexplained recurrent fever and poor effect of non-steroidal anti-inflammatory drugs, especially with the symptoms of no sweating and insensitivity to pain, the possibility of Marsili syndrome should be considered and the ZFHX2 gene should be determined. Marsili syndrome appears to be a benign disease with a good prognosis. A definitive diagnosis can avoid ineffective treatment and its adverse effects. To our knowledge, there is currently no effective genetic therapy for this disease.

Genetic pain loss disorders.

Genetic pain loss includes congenital insensitivity to pain (CIP), hereditary sensory neuropathies and, if autonomic nerves are involved, hereditary sensory and autonomic neuropathy (HSAN). This heterogeneous group of disorders highlights the essential role of nociception in protecting against tissue damage. Patients with genetic pain loss have recurrent injuries, burns and poorly healing wounds as disease hallmarks. CIP and HSAN are caused by pathogenic genetic variants in >20 genes that lead to developmental defects, neurodegeneration or altered neuronal excitability of peripheral damage-sensing neurons. These genetic variants lead to hyperactivity of sodium channels, disturbed haem metabolism, altered clathrin-mediated transport and impaired gene regulatory mechanisms affecting epigenetic marks, long non-coding RNAs and repetitive elements. Therapies for pain loss disorders are mainly symptomatic but the first targeted therapies are being tested. Conversely, chronic pain remains one of the greatest unresolved medical challenges, and the genes and mechanisms associated with pain loss offer new targets for analgesics. Given the progress that has been made, the coming years are promising both in terms of targeted treatments for pain loss disorders and the development of innovative pain medicines based on knowledge of these genetic diseases.

Structural analysis of TrkA mutations in patients with congenital insensitivity to pain reveals PLCγ as an analgesic drug target.

Chronic pain is a major health issue, and the search for new analgesics has become increasingly important because of the addictive properties and unwanted side effects of opioids. To explore potentially new drug targets, we investigated mutations in the NTRK1 gene found in individuals with congenital insensitivity to pain with anhidrosis (CIPA). NTRK1 encodes tropomyosin receptor kinase A (TrkA), the receptor for nerve growth factor (NGF) and that contributes to nociception. Molecular modeling and biochemical analysis identified mutations that decreased the interaction between TrkA and one of its substrates and signaling effectors, phospholipase Cγ (PLCγ). We developed a cell-permeable phosphopeptide derived from TrkA (TAT-pQYP) that bound the Src homology domain 2 (SH2) of PLCγ. In HEK-293T cells, TAT-pQYP inhibited the binding of heterologously expressed TrkA to PLCγ and decreased NGF-induced, TrkA-mediated PLCγ activation and signaling. In mice, intraplantar administration of TAT-pQYP decreased mechanical sensitivity in an inflammatory pain model, suggesting that targeting this interaction may be analgesic. The findings demonstrate a strategy to identify new targets for pain relief by analyzing the signaling pathways that are perturbed in CIPA.

[Novel compound heterozygous SCN9A variations causing congenital insensitivity to pain in a patient].

OBJECTIVE: To explore the genetic basis for a child featuring congenital insensitivity to pain (CIP). METHODS: Targeted capture and next generation sequencing (NGS) was carried out for the proband. Suspected pathogenic variants were confirmed by Sanger sequencing of the proband and his parents. RESULTS: The proband was found to harbor compound heterozygous variants of SCN9A gene, namely c.1598delA (p.N533Ifs*31) and c.295_296delCGinsAT (p.R99I), which were respectively inherited from his father and mother. Both variants were predicted to be pathogenic, and neither was reported previously. CONCLUSION: The compound heterozygous variants of the SCN9A gene probably underlay the CIP in this child. Above finding has enabled genetic counseling for this family.

Nav1.7 is required for normal C-low threshold mechanoreceptor function in humans and mice.

Patients with bi-allelic loss of function mutations in the voltage-gated sodium channel Nav1.7 present with congenital insensitivity to pain (CIP), whilst low threshold mechanosensation is reportedly normal. Using psychophysics (n = 6 CIP participants and n = 86 healthy controls) and facial electromyography (n = 3 CIP participants and n = 8 healthy controls), we found that these patients also have abnormalities in the encoding of affective touch, which is mediated by the specialized afferents C-low threshold mechanoreceptors (C-LTMRs). In the mouse, we found that C-LTMRs express high levels of Nav1.7. Genetic loss or selective pharmacological inhibition of Nav1.7 in C-LTMRs resulted in a significant reduction in the total sodium current density, an increased mechanical threshold and reduced sensitivity to non-noxious cooling. The behavioural consequence of loss of Nav1.7 in C-LTMRs in mice was an elevation in the von Frey mechanical threshold and less sensitivity to cooling on a thermal gradient. Nav1.7 is therefore not only essential for normal pain perception but also for normal C-LTMR function, cool sensitivity and affective touch.

Congenital insensitivity to pain: a novel mutation affecting a U12-type intron causes multiple aberrant splicing of SCN9A.

ABSTRACT: Mutations in the alpha subunit of voltage-gated sodium channel 1.7 (NaV1.7), encoded by SCN9A gene, play an important role in the regulation of nociception and can lead to a wide range of clinical outcomes, ranging from extreme pain syndromes to congenital inability to experience pain. To expand the phenotypic and genotypic spectrum of SCN9A-related channelopathies, we describe the proband, a daughter born from consanguineous parents, who had pain insensitivity, diminished temperature sensation, foot burns, and severe loss of nociceptive nerve fibers in the epidermis. Next-generation sequencing of SCN9A (NM_002977.3) revealed a novel homozygous substitution (c.377+7T>G) in the donor splice site of intron 3. As the RNA functional testing is challenging, the in silico analysis is the first approach to predict possible alterations. In this case, the computational analysis was unable to identify the splicing consensus and could not provide any prediction for splicing defects. The affected intron indeed belongs to the U12 type, a family of introns characterised by noncanonical consensus at the splice sites, accounting only for 0.35% of all human introns, and is not included in most of the training sets for splicing prediction. A functional study on proband RNA showed different aberrant transcripts, where exon 3 was missing and an intron fragment was included. A quantification study using real-time polymerase chain reaction showed a significant reduction of the NaV1.7 canonical transcript. Collectively, these data widen the spectrum of SCN9A-related insensitivity to pain by describing a mutation causing NaV1.7 deficiency, underlying the nociceptor dysfunction, and highlight the importance of molecular investigation of U12 introns' mutations despite the silent prediction.

Identification of novel variations in the NTRK1 gene causing congenital insensitivity to pain with anhidrosis.

BACKGROUND: Congenital insensitivity to pain (CIP) conditions are a group of Mendelian disorders with clinical and genetic heterogeneity. CIP with anhidrosis (CIPA) is a distinct subtype caused by biallelic variants in the NTRK1 gene. METHODS: In this study, six families with CIPA were recruited and submitted to a series of clinical and genetic examinations. Whole-exome sequencing and whole-genome sequencing were applied to perform a comprehensive genetic analysis. Sanger sequencing was used as a validation method. RESULTS: These patients exhibited phenotypic variability. All probands in the six families were positive for biallelic pathogenic variants in NTRK1. Five individual variants, namely NTRK1: (NM_002529.3) c.851-33T>A, c.717+2T>C, c.1806-2A>G, c.1251+1G>A, and c.851-794C>G, including three novel ones, were identified, which were carried by the six patients in a homozygous or compound heterozygous way. The validation results indicated that all the parents of the six probands, except for one father and one mother, were monoallelic carriers of a single variant. CONCLUSIONS: The findings in our study extended the variation spectrum of the NTRK1 gene and highlighted the advantage of the integrated application of multiplatform genetic technologies.

Rare mutations in ATL3, SPTLC2 and SCN9A explaining hereditary sensory neuropathy and congenital insensitivity to pain in a Brazilian cohort.

Hereditary sensory neuropathies (HSN) are a group of rare neurological disorders with heterogeneous clinical and genetic characteristics. Although at least 17 different genes have already been associated with HSN, the epidemiology of the disorder in Brazil is still unknown. Performing whole genome sequencing (WGS) in 23 unrelated Brazilian families diagnosed with HSN, we detected pathogenic variants in ATL3, SPTLC2, and SCN9A in 12 patients belonging to five unrelated families. Clinical features associated with heterozygous mutations in ATL3 (c.575A > G; p.(Tyr192Cys)) and SPTLC2 (c.529A > G; p.(Asn177Asp)) were sensory deficits, neuropathic pain, and recurrent ulcerations. Presenting as congenital insensitivity to pain, three unrelated probands carried biallelic loss-of-function mutations in SCN9A. The so far undescribed stop mutation c.2106G > A (p.(Trp702Ter)) and the likewise novel splicing variant c.3319-1G > A were found in compound-heterozygosity with, respectively, the known pathogenic variants c.2908G > T (p.Trp970Ter) and c.2690G > A (p.Glu897Ter). In total, we identified pathogenic mutations in 21.7% of our families, which suggests that most of the cases could be explained by yet to be discovered genes or unusual alleles. Our study represents the first mutational screen in a Brazilian HSN cohort, enabling additional insights for genotype-phenotype correlations, reducing misdiagnoses, and providing early treatment considerations.

Loss of Prdm12 during development, but not in mature nociceptors, causes defects in pain sensation.

Prdm12 is a key transcription factor in nociceptor neurogenesis. Mutations of Prdm12 cause congenital insensitivity to pain (CIP) from failure of nociceptor development. However, precisely how deletion of Prdm12 during development or adulthood affects nociception is unknown. Here, we employ tissue- and temporal-specific knockout mouse models to test the function of Prdm12 during development and in adulthood. We find that constitutive loss of Prdm12 causes deficiencies in proliferation during sensory neurogenesis. We also demonstrate that conditional knockout from dorsal root ganglia (DRGs) during embryogenesis causes defects in nociception. In contrast, we find that, in adult DRGs, Prdm12 is dispensable for most pain-sensation and injury-induced hypersensitivity. Using transcriptomic analysis, we find mostly unique changes in adult Prdm12 knockout DRGs compared with embryonic knockout and that PRDM12 is likely a transcriptional activator in the adult. Overall, we find that the function of PRDM12 changes over developmental time.

Perception of pungent, gustatory and olfactory stimuli in patients with congenital insensitivity to pain with anhidrosis.

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare disease caused by a mutation in the nerve growth factor (NGF) receptor, which results in an absence of Aδ and C fibers. It can be considered that this defect may also lead to deterioration of oral sensations. The aim of the present study was to clarify the ability of CIPA patients to perceive pungent, gustatory, and olfactory stimuli, which is essential for eating function, and the impact of the defect on dietary habits. Sensitivities to capsaicin and the five basic tastes were evaluated by measuring their threshold values, and dietary habits were examined using a questionnaire. Additionally, odor identification ability was evaluated using the odor stick method. The detection threshold for capsaicin and the recognition threshold for sour taste were significantly higher in the patients than in healthy volunteers. The questionnaire responses showed that the patients consumed spicy food more often. All patients were able to identify the tested odors, except those to which they had not been well accustomed. Since the abilities of CIPA patients to perceive taste and smell were not basically impaired, despite their lower sensitivity to capsaicin, it was suggested that their dietary habits were only minimally affected, except for intake of pungent foods.