AAV-Mediated Gene Therapy for Glycosphingolipid Biosynthesis Deficiencies.

De novo glycosphingolipid (GSL) biosynthesis defects cause severe neurological diseases, including hereditary sensory and autonomic neuropathy type 1A (HSAN1A), GM3 synthase deficiency, and hereditary spastic paraplegia type 26 (HSPG26), each lacking effective treatment. Recombinant adeno-associated virus (AAV)-mediated gene therapy has emerged as a powerful treatment for monogenic diseases and might be particularly suitable for these neurological conditions.

Hereditary sensory autonomic neuropathy Type VIII: A rare clinical presentation, genomics, diagnosis, and management in an infant.

A 7-month-old female child born to nonconsanguineous parents with a history of global developmental delay, since early infancy had reported to the department with facial features of mild dysmorphism. History of finger sucking and finger biting was evident, as there was a massive scab tissue over the dorsal aspect of the index finger, above the finger nail bed. A huge ulcer was evident on the right side of the dorsal aspect of anterior two-thirds of the tongue. Genetic evaluation through targeted gene sequencing confirmed the diagnosis as hereditary sensory, autonomic neuropathy Type VIII (Online Mendelian Inheritance in Man - 616488). A homozygous missense variation in exon 3 of PRDM12 was detected. A multidisciplinary approach was planned for the management of the child. A soft splint on the maxilla was fabricated and stabilized with an adhesive. However, the final diagnosis was confirmed by a DNA genomic sequencing test, namely a multigene panel testing or comprehensive genomic sequencing.

Cholinergic striatal neurons are increased in HSAN V homozygous mice despite reduced NGF bioavailability.

The neurotrophin Nerve growth factor (NGF) plays a critical role in the mature and developing nervous system. A point mutation (R100W) in the NGFB gene was found in patients with Hereditary Sensory and Autonomic Neuropathy type V (HSAN V), which leads to pain insensitivity. In a previous work it has been shown that the mutation provokes a reduced secretion of mature NGF. In this study we generated and analyzed homozygous NGFR100W/R100W mice to understand whether the reduced NGF bioavailability can contribute to the clinical phenotype of the homozygous condition. We found that the majority of NGFR100W/R100W mice were born normal but failed to reach the first month of age. This early lethality was rescued by daily treatment with wild type NGF. In addition, we found that the density of cholinergic neurons of homozygous mice was unaffected in the medial septum and in the nucleus basalis of Meynert, whereas, suprisingly, it was increased specifically in the striatum. Due to the known action of the striatal cholinergic tone in modulating pain, our findings support the hypothesis that a central mechanism, linked to the NGFR100W-dependent increase of the striatal cholinergic tone, can contribute to the pain insensitivity observed in HSAN V patients.

A Case of Congenital Insensitivity to Pain With Anhidrosis Comorbid With Attention Deficit Hyperactivity Disorder: Clinical Implications for Pathophysiology and Treatment.

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autosomal recessive genetic disorder caused by a mutation in the neurotrophic tyrosine kinase receptor (NTRK1) gene. CIPA is accompanied by abnormal catecholamine metabolism and decreased blood concentration of dopamine and norepinephrine. Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder of heterogeneous etiology and presentation, and recent reports have suggested a pathophysiological role of neurotrophins in ADHD. Furthermore, dopamine and norepinephrine are known to play major roles in the pathophysiology of ADHD, and the imbalance of monoaminergic and cholinergic systems as an underlying cause of ADHD has recently been studied. Here, we report the case of an 11-year-old boy with CIPA and comorbid ADHD. Our observations have important clinical implications for patients with CIPA. Because of deficiencies in self-control, proper management of these patients necessitates a highly structured and monitored environment, made dually important by possible comorbidity of ADHD.

An Innovative Cooling Jacket to Combat Heat Intolerance in Children with Anhidrosis.

Hyperthermia and heat intolerance are distressing symptoms in patients with anhidrosis. Body cooling devices are an integral part of management of these patients. A cooling jacket made from easily available materials has been invented for a girl with congenital insensitivity to pain and anhidrosis with severe heat intolerance. This innovative cooling jacket may be helpful for anhidrotic children in resource-poor situations.

Orthopaedic manifestations of congenital indifference to pain with anhidrosis (Hereditary Sensory and Autonomic Neuropathy type IV).

BACKGROUND: Congenital indifference to pain with anhidrosis (CIPA) is a rare hereditary neuropathy, which is associated with defective sensation to noxious stimuli and autonomic dysfunction. The objective of the study was to report on the orthopaedic manifestations of this condition and provide an evidence-based approach for management. METHODS: Retrospective review of 14 consecutive patients with CIPA referred to a single tertiary centre. Mean age of diagnosis was 2.5 years (range 0.5 to 11 years). RESULTS: Patients presented with a range of orthopaedic problems including fractures, infections, growth disturbance, joint subluxation and Charcot joints affecting the limbs and spine. Conservative treatment with closed reduction and cast immobilisation was satisfactory for stress fractures of the lower extremity and Charcot joints. Posterior instrumented correction of scoliosis was associated with a high-risk of infection requiring reoperation for debridement and removal of posterior instrumentation. Growth disturbance leading to leg-length discrepancies were managed with shoe raises and corrective osteotomies. Aspiration and cultures may be used to differentiate between acute fracture and infection. CONCLUSIONS: Preventative treatment strategies with appropriately padded shoe-wear, gait and posture modification, parental education regarding environmental thermoregulation, and behavioural support are essential for improving prognosis and reducing long-term complications.

Congenital insensitivity to pain with anhidrosis: A report of two siblings with a novel mutation in (TrkA) NTRK1 gene in a Saudi family.

Congenital insensitivity to pain with anhidrosis (CIPA) or hereditary sensory and autonomic neuropathy type IV (HSAN type IV) is an extremely rare autosomal recessive disorder with an estimated incidence of 1 in 25,000. It was first described in 1963, and since then several case reports and review articles have been published. In this article, we report two brothers with clinical features of CIPA, who presented with recurrent episodes of hyperthermia, anhidrosis, profound loss of pain sensitivity, and unconscious self-mutilation of fingers, lip and tongue. Sanger sequencing analysis confirmed the presence of a novel mutation c.783_785delGAA in the NTRK1 gene in the two affected members of the family. Early diagnosis and management of different systemic complications including orthopedic, visual, and dental may be useful in the reduction of frequency and severity of these complications.

Molecular pathogenesis, experimental therapy and genetic counseling in hereditary sensory neuropathies.

Hereditary sensory and autonomic neuropathies (HSANs) represent a group of heritable peripheral nerve disorders usually taking a severe clinical course. HSAN-affected patients manifest with deep, poorly-healing ulcerations of the feet and hands. To date no definitive cure for HSANs has been developed and the molecular pathology of these disorders is complex. The aim of this review is therefore to present recent findings in terms of HSAN molecular pathogenesis. So far, mutations in 12 genes coding for different proteins have been reported in association with HSAN and the molecular pathogenesis has been elucidated in HSAN1a, HSAN4 and HSAN5. The genes involved in molecular pathogenesis of HSAN code for a wide spectrum of proteins from enzymes to specific nerve growth factors. As far as HSAN1a is concerned, the enhanced understanding has given rise to achievements in experimental therapy particularly in respect to disease models. Despite a rapid progress in studies on the molecular background of HSAN, numerous loci and genes remain still to be discovered.

Hereditary motor and sensory neuropathies: Understanding molecular pathogenesis could lead to future treatment strategies.

Inherited peripheral neuropathies, like many other degenerative disorders, have been challenging to treat. At this point, there is little specific therapy for the inherited neuropathies other than genetic counseling as well as symptomatic treatment and rehabilitation. In the past, ascorbic acid, progesterone antagonists, and subcutaneous neurotrophin-3 (NT3) injections have demonstrated improvement in animal models of CMT 1A, the most common inherited neuropathy, but have failed to translate any effect in humans. Given the difficulty in treatment, it is important to understand the molecular pathogenesis of hereditary neuropathies in order to strategize potential future therapies. The hereditary neuropathies are in an era of molecular insight and over the past 20 years, more than 78 subtypes of Charcot Marie Tooth disease (CMT) have been identified and extensively studied to understand the biological pathways in greater detail. Next generation molecular sequencing has also improved the diagnosis as well as the understanding of CMT. A greater understanding of the molecular pathways will help pave the way to future therapeutics of CMT. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

Pediatric neuropathic arthropathy initially masquerading as inflammatory arthritis.

We describe a case of neuropathic arthropathy in the knees of a child eventually diagnosed with a hereditary sensory and autonomic neuropathy. The child was initially treated for rheumatologic disease at an outside institution. History and neurological workup revealed a neuropathy most consistent with hereditary sensory and autonomic neuropathy type II. Hereditary sensory and autonomic neuropathy should be considered in the differential diagnosis of children with joint abnormalities whose workup for an inflammatory arthropathy is negative and who exhibit diminished pain sensation on examination.

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.

Diagnosis and new treatments in genetic neuropathies.

The genetic neuropathies are a clinically and genetically heterogeneous group of diseases of which the most common types are Charcot-Marie-Tooth disease (CMT), the hereditary sensory and autonomic neuropathies and the distal hereditary motor neuropathies. More than 30 causative genes have been described, making an accurate genetic diagnosis increasingly possible. Although no specific therapies are yet available, research into their pathogenesis has revolutionised our understanding of the peripheral nervous system and allowed the development of rational approaches to therapy. The first therapeutic trials in CMT are currently underway. This review will suggest an approach to the diagnosis of these disorders and provide an update on new therapies.

Hereditary sensory neuropathy type I.

Hereditary sensory neuropathy type I (HSN I) is a slowly progressive neurological disorder characterised by prominent predominantly distal sensory loss, autonomic disturbances, autosomal dominant inheritance, and juvenile or adulthood disease onset. The exact prevalence is unknown, but is estimated as very low. Disease onset varies between the 2nd and 5th decade of life. The main clinical feature of HSN I is the reduction of sensation sense mainly distributed to the distal parts of the upper and lower limbs. Variable distal muscle weakness and wasting, and chronic skin ulcers are characteristic. Autonomic features (usually sweating disturbances) are invariably observed. Serious and common complications are spontaneous fractures, osteomyelitis and necrosis, as well as neuropathic arthropathy which may even necessitate amputations. Some patients suffer from severe pain attacks. Hypacusis or deafness, or cough and gastrooesophageal reflux have been observed in rare cases. HSN I is a genetically heterogenous condition with three loci and mutations in two genes (SPTLC1 and RAB7) identified so far. Diagnosis is based on the clinical observation and is supported by a family history. Nerve conduction studies confirm a sensory and motor neuropathy predominantly affecting the lower limbs. Radiological studies, including magnetic resonance imaging, are useful when bone infections or necrosis are suspected. Definitive diagnosis is based on the detection of mutations by direct sequencing of the SPTLC1 and RAB7 genes. Correct clinical assessment and genetic confirmation of the diagnosis are important for appropriate genetic counselling and prognosis. Differential diagnosis includes the other hereditary sensory and autonomic neuropathies (HSAN), especially HSAN II, as well as diabetic foot syndrome, alcoholic neuropathy, neuropathies caused by other neurotoxins/drugs, immune mediated neuropathy, amyloidosis, spinal cord diseases, tabes dorsalis, lepra neuropathy, or decaying skin tumours like amelanotic melanoma. Management of HSN I follows the guidelines given for diabetic foot care (removal of pressure to the ulcer and eradication of infection, followed by the use of specific protective footwear) and starts with early and accurate counselling of patients about risk factors for developing foot ulcerations. The disorder is slowly progressive and does not influence life expectancy but is often severely disabling after a long duration of the disease.

Hereditary sensory and autonomic neuropathies: types II, III, and IV.

The hereditary sensory and autonomic neuropathies (HSAN) encompass a number of inherited disorders that are associated with sensory dysfunction (depressed reflexes, altered pain and temperature perception) and varying degrees of autonomic dysfunction (gastroesophageal reflux, postural hypotention, excessive sweating). Subsequent to the numerical classification of four distinct forms of HSAN that was proposed by Dyck and Ohta, additional entities continue to be described, so that identification and classification are ongoing. As a group, the HSAN are rare diseases that affect both sexes. HSAN III is almost exclusive to individuals of Eastern European Jewish extraction, with incidence of 1 per 3600 live births. Several hundred cases with HSAN IV have been reported. The worldwide prevalence of HSAN type II is very low. This review focuses on the description of three of the disorders, HSAN II through IV, that are characterized by autosomal recessive inheritance and onset at birth. These three forms of HSAN have been the most intensively studied, especially familial dysautonomia (Riley-Day syndrome or HSAN III), which is often used as a prototype for comparison to the other HSAN. Each HSAN disorder is likely caused by different genetic errors that affect specific aspects of small fiber neurodevelopment, which result in variable phenotypic expression. As genetic tests are routinely used for diagnostic confirmation of HSAN III only, other means of differentiating between the disorders is necessary. Diagnosis is based on the clinical features, the degree of both sensory and autonomic dysfunction, and biochemical evaluations, with pathologic examinations serving to further confirm differences. Treatments for all these disorders are supportive.

Spinal anesthesia in a patient with congenital insensitivity to pain with anhidrosis.

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare, hereditary, autonomic recessive disorder. The inability to perceive pain results from loss of nociceptive afferents, while anhidrosis is caused by loss of innervation to the sweat glands. Insensitivity to pain and mental retardation lead to self-inflicted injuries, corneal lacerations, painless bony fractures, joint deformities with consequent chronic osteomyelitis, and septic arthritis. There are only a few reports on the anesthetic management for patients with CIPA. We describe the anesthetic management of a young woman with CIPA receiving bilateral arthrodesis of the ankle.

Hereditary sensory neuropathies.

Hereditary sensory neuropathies (HSNs) are a group of genetically determined peripheral neuropathies with prominent disturbance of the peripheral sensory neurons. They are characterized by sensory loss, insensitivity to pain, a variable degree of muscle weakness and wasting, as well as autonomic features. Frequent complications are foot ulcerations and infections that may lead to osteomyelitis, followed by necrosis and amputations. Consequently, the hereditary sensory neuropathies have also been termed ulceromutilating neuropathies. On the other hand, in the presence of additional motor weakness, they have been subclassified among the group of Charcot-Marie-Tooth (CMT) disorders. Sporadic and familial cases with different modes of inheritance are known to affect both children and adults. The most prevalent forms of the autosomal dominantly inherited hereditary sensory neuropathies are HSN I and CMT 2b. HSN I is associated with mutations in the SPTLC1 gene, whereas mutations in the RAB7 gene have been identified in CMT 2b. However, at least one more hitherto unknown gene responsible for autosomal-dominant hereditary sensory neuropathies must exist. Autosomal-recessive hereditary sensory neuropathies types III and IV, and probably also type V, result from mutations in the IKBKAP and NTRK1 genes. Very recently, the gene in HSN II (HSN2) has been identified. A spontaneous autosomal-recessive mutation in the Cct4 gene has been reported in the Sprague-Dawley rat strain with early onset sensory neuropathy. Although no curative treatment is available so far, and current therapy is limited to symptom relief, these molecular genetic advances in knowledge about the hereditary sensory neuropathies can be translated into clinical practice by improving diagnosis and genetic counseling. They will also be the basis for functional studies in the future.