A short in-frame deletion in NTRK1 tyrosine kinase domain caused by a novel splice site mutation in a patient with congenital insensitivity to pain with anhidrosis

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.

Wilson Disease Comorbid with Hereditary Sensory Autonomic Neuropathy Type IV and Gitelman Syndrome

Wilson disease a rare autosomal recessive inherited disorder of copper metabolism, is characterized by excessive deposition of copper in the liver, brain, and other tissues. Wilson disease is often fatal if it is not recognized early and treated when it is symptomatic. Gitelman syndrome is also an autosomal recessive kidney disorder characterized by low blood levels of potassium and magnesium, decreased excretion of calcium in the urine, and elevated blood pH. Hereditary sensory autonomic neuropathy type IV (HSAN-IV), a very rare condition that presents in infancy, is characterized by anhidrosis, absence of pain sensation, and self-mutilation. It is usually accompanied by developmental delay and mental retardation. We report a case of Wilson disease manifested as fulminant hepatitis, acute pancreatitis, and acute kidney injury in a 15-year-old boy comorbid with HSAN-IV and Gitelman syndrome. Such concurrence of three genetic diseases is an extremely rare case.

Heterotopic ossifications and Charcot joints: Congenital insensitivity to pain with anhidrosis (CIPA) and a novel NTRK1 gene mutation

Congenital insensitivity to pain with anhidrosis (CIPA), also known as hereditary sensory and autonomic neuropathy type IV (HSAN-IV), is a rare and severe autosomal recessive disorder. We report on an adult female patient whose clinical findings during childhood were not recognized as CIPA. There was neither complete anhidrosis nor a recognizable sensitivity to heat. Tumorlike swellings of many joints and skeletal signs of Charcot neuropathy developed in adolescence which, together with a history of self-mutilation, led to a clinical suspicion of CIPA confirmed by identification of a novel homozygous variant c.1795G > T in the NTRK1 gene in blood lymphocytes. Both parents were heterozygous for the mutation. The variant predicts a premature stop codon (p.Gly599Ter) and thus represents a pathogenic variant; the first reported in the Southeastern European population.

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.

Phenotypic heterogeneity of intellectual disability in patients with congenital insensitivity to pain with anhidrosis: A case report and literature review

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autosomal recessive heterogeneous disorder mainly caused by mutations in the neurotrophic tyrosine receptor kinase 1 gene (NTRK1) and characterized by insensitivity to noxious stimuli, anhidrosis, and intellectual disability. We herein report the first north Han Chinese patient with CIPA who exhibited classic phenotypic features and severe intellectual disability caused by a homozygous c.851-33T>A mutation of NTRK1, resulting in aberrant splicing and an open reading frame shift. We reviewed the literature and performed in silico analysis to determine the association between mutations and intellectual disability in patients with CIPA. We found that intellectual disability was correlated with the specific Ntrk1 protein domain that a mutation jeopardized. Mutations located peripheral to the Ntrk1 protein do not influence important functional domains and tend to cause milder symptoms without intellectual disability. Mutations that involve critical amino acids in the protein are prone to cause severe symptoms, including intellectual disability.

Mutations in TrkA Causing Congenital Insensitivity to Pain with Anhidrosis (CIPA) Induce Misfolding, Aggregation, and Mutation-dependent Neurodegeneration by Dysfunction of the Autophagic Flux

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autosomal recessive disorder characterized by insensitivity to noxious stimuli and variable intellectual disability (ID) due to mutations in the NTRK1 gene encoding the NGF receptor TrkA. To get an insight in the effect of NTRK1 mutations in the cognitive phenotype we biochemically characterized three TrkA mutations identified in children diagnosed of CIPA with variable ID. These mutations are located in different domains of the protein; L213P in the extracellular domain, Δ736 in the kinase domain, and C300stop in the extracellular domain, a new mutation causing CIPA diagnosed in a Spanish teenager. We found that TrkA mutations induce misfolding, retention in the endoplasmic reticulum (ER), and aggregation in a mutation-dependent manner. The distinct mutations are degraded with a different kinetics by different ER quality control mechanisms; although C300stop is rapidly disposed by autophagy, Δ736 degradation is sensitive to the proteasome and to autophagy inhibitors, and L213P is a long-lived protein refractory to degradation. In addition L213P enhances the formation of autophagic vesicles triggering an increase in the autophagic flux with deleterious consequences. Mouse cortical neurons expressing L213P showed the accumulation of LC3-GFP positive puncta and dystrophic neurites. Our data suggest that TrkA misfolding and aggregation induced by some CIPA mutations disrupt the autophagy homeostasis causing neurodegeneration. We propose that distinct disease-causing mutations of TrkA generate different levels of cell toxicity, which may provide an explanation of the variable intellectual disability observed in CIPA patients.

Congenital insensitivity to pain with anhidrosis in Sudanese children

Congenital insensitivity to pain with anhidrosis (CIPA), also called hereditary sensory and autonomic neuropathy type IV (HSAN-IV), is an extremely rare autosomal recessive disease. It is characterized by insensitivity to pain, inability to sweat, episodes of hyperpyrexia, and intellectual disability. These factors render the affected persons to repeatedly injure and traumatise themselves to the degree that they become disabled. No specific treatment to the moment, but it needs multidisciplinary approach, and certain life adaptations and education. Here we report 4 unrelated Sudanese children affected with this rare neurological disorder, to raise the awareness on this rare disease, reflecting its spectrum, and the challenges which patients and their families face, especially when living in a hot country.

Novel NTRK1 Frameshift Mutation in Congenital Insensitivity to Pain With Anhidrosis

Congenital insensitivity to pain with anhidrosis is a rare autosomal recessive disorder. It has been reported that the defect in the NTRK1 gene encoding tropomyosin-related kinase A (TrkA) can cause congenital insensitivity to pain with anhidrosis. Nerve growth factor (NGF), the product of NGFB, mediates biological effects by binding to and activating tropomyosin-related kinase A. In addition, necdin (encoded by NDN) is also essential in nerve growth factor-tropomyosin-related kinase A pathway. We performed mutation analysis in NTRK1, NGFB, and NDN genes in a Chinese Han 17-year-old female patient with congenital insensitivity to pain with anhidrosis and her healthy family members. As a result, the patient was found to have a novel insertion in exon 7 (c.727insT) of NTRK1, which causes premature termination, and a single nucleotide polymorphism (rs2192206 G>A) in NDN. Our findings imply that the genetic variations of the nerve growth factor-tropomyosin-related kinase A pathway play an important role in congenital insensitivity to pain with anhidrosis.

Twins with hereditary sensory and autonomic neuropathy type IV with preserved periodontal sensation

Turkish twin brothers affected with hereditary sensory and autonomic neuropathy type IV (HSAN IV) are reported. Their clinical findings were generally typical for HSAN IV. Interestingly they both had preserved periodontal sensation. Mutation analysis of the NTRK1 gene showed a homozygous c.2001C>T substitution in exon 15 in both twins. This base substitution is predicted to change a polar, positively charged amino acid arginine to the highly active amino acid cystein at position 654 (p.Arg654Cys). The parents were heterozygous for the mutation. This mutation has been reported previously in one Japanese and one Arab patients. The preserved periodontal sensation has not previously been reported in patients affected with HSAN IV. This preserved sensation in our patients might have been through Ruffini endings, the periodontal mechanoreceptors which have been reported to be present in TrkA knockout mice. Here we report the first twins affected with HSAN IV and the observation that periodontal sensation is not affected by mutation in NTRK1.

Congenital insensitivity to pain with anhidrosis presenting with palmoplantar keratoderma

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autosomal-recessive disease caused by mutations in the NTRK1 gene. The disease is characterized by insensitivity to pain and absence of thermal perception. Herein a 6-year-old boy is presented with a large ulcer on the sole of his right foot and a thick, hyperkeratotic appearance of his palms and soles; there was also a medical history of hyperthermia, anhidrosis, recurrent bone fractures, osteomyelitis, injuries, mental retardation, dry and exfoliative skin, insensitivity to pain, and lack of thermal sensation. Genetic studies revealed a homozygote mutation in the NTRK1 gene. Although the patient initially presented with palmoplantar keratoderma, genetic studies confirmed the diagnosis of CIPA.

Nerve growth factor-mediated regulation of pain signalling and proposed new intervention strategies in clinical pain management

Nerve growth factor (NGF) is the founding member of the neurotrophins family of proteins. It was discovered more than half a century ago through its ability to promote sensory and sympathetic neuronal survival and axonal growth during the development of the peripheral nervous system, and is the paradigmatic target-derived neurotrophic factor on which the neurotrophic hypothesis is based. Since that time, NGF has also been shown to play a key role in the generation of acute and chronic pain and in hyperalgesia in diverse pain states. NGF is expressed at high levels in damaged or inflamed tissues and facilitates pain transmission by nociceptive neurons through a variety of mechanisms. Genetic mutations in NGF or its tyrosine kinase receptor TrkA, lead to a congenital insensitivity or a decreased ability of humans to perceive pain. The hereditary sensory autonomic neuropathies (HSANs) encompass a spectrum of neuropathies that affect one's ability to perceive sensation. HSAN type IV and HSAN type V are caused by mutations in TrkA and NGF respectively. This review will focus firstly on the biology of NGF and its role in pain modulation. We will review neuropathies and clinical presentations that result from the disruption of NGF signalling in HSAN type IV and HSAN type V and review current advances in developing anti-NGF therapy for the clinical management of pain.

Old fractures in two patients with congenital insensitivity to pain with anhidrosis: radiological findings

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autosomal recessive disease that is characterized by anhidrosis, insensitivity to noxious stimuli, and mental retardation. Patients who suffer from CIPA easily sustain injuries due to pain insensitivity. Radiological findings in two CIPA patients revealed several old fractures of which the patients were unaware of previous injury. An early diagnosis of CIPA is important for the prevention and treatment of various complications. Our data indicate that radiological findings may provide important information for the diagnosis of CIPA.

Mechanisms of disease in hereditary sensory and autonomic neuropathies

Hereditary sensory and autonomic neuropathies (HSANs) are a clinically and genetically heterogeneous group of disorders of the PNS. Progressive degeneration, predominantly of sensory and autonomic neurons, is the main pathological feature in patients with HSAN, and causes prominent sensory loss and ulcerative mutilations in combination with variable autonomic and motor disturbances. Advances in molecular genetics have enabled identification of disease-causing mutations in 12 genes, and studies on the functional effects of these mutations are underway. Although some of the affected proteins--such as nerve growth factor and its receptor--have obvious nerve-specific roles, others are ubiquitously expressed proteins that are involved in sphingolipid metabolism, vesicular transport, transcription regulation and structural integrity. An important challenge in the future will be to understand the common molecular pathways that result in HSANs. Unraveling the mechanisms that underlie sensory and autonomic neurodegeneration could assist in identifying targets for future therapeutic strategies in patients with HSAN. This Review highlights key advances in the understanding of HSANs, including insights into the molecular mechanisms of disease, derived from genetic studies of patients with these disorders.

Receptor tyrosine kinases: from biology to pathology

Receptor tyrosine kinases (RTKs) are transmembrane proteins involved in the control of fundamental cellular processes in metazoans. RTKs possess a general structure that includes an extracellular domain, a transmembrane domain and a highly conserved tyrosine kinase domain. RTKs are classified according to their variable extracellular ligand-binding domain. Studies of human RTK members have yielded a wealth of information elucidating their importance. Improper functioning of these enzymes due to mutations, mainly in the kinase domain, is often manifested in various human diseases and is known to be involved in several types of cancer. Here we summarize most of human RTKs, their cognate ligands, as well as related diseases and discuss the eventual use of certain RTKs as new therapeutic targets.