RESUMEN
BACKGROUND: A comprehensive understanding of the genetic basis of rare diseases and their regulatory mechanisms is essential for human molecular genetics. However, the genetic mutant spectrum of pathogenic genes within the Chinese population remains underrepresented. Here, we reported previously unreported functional ABHD12 variants in two Chinese families and explored the correlation between genetic polymorphisms and phenotypes linked to PHARC syndrome. METHODS: Participants with biallelic pathogenic ABHD12 variants were recruited from the Chinese Deafness Genetics Cohort. These participants underwent whole-genome sequencing. Subsequently, a comprehensive literature review was conducted. RESULTS: Two Han Chinese families were identified, one with a compound heterozygous variant and the other with a novel homozygous variant in ABHD12. Among 65 PHARC patients, including 62 from the literature and 3 from this study, approximately 90% (57 out of 63) exhibited hearing loss, 82% (50 out of 61) had cataracts, 82% (46 out of 56) presented with retinitis pigmentosa, 79% (42 out of 53) experienced polyneuropathy, and 63% (36 out of 57) displayed ataxia. Seventeen different patterns were observed in the five main phenotypes of PHARC syndrome. A total of 33 pathogenic variants were identified in the ABHD12. Compared with other genotypes, individuals with biallelic truncating variants showed a higher incidence of polyneuropathy (p = 0.006), but no statistically significant differences were observed in the incidence of hearing loss, ataxia, retinitis pigmentosa and cataracts. CONCLUSIONS: The diagnosis of PHARC syndrome is challenging because of its genetic heterogeneity. Therefore, exploring novel variants and establishing genotype-phenotype correlations can significantly enhance gene diagnosis and genetic counseling for this complex disease.
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Ataxia , Catarata , Estudios de Asociación Genética , Monoacilglicerol Lipasas , Linaje , Fenotipo , Polineuropatías , Retinitis Pigmentosa , Humanos , Masculino , Femenino , Ataxia/genética , Catarata/genética , Retinitis Pigmentosa/genética , Retinitis Pigmentosa/patología , Polineuropatías/genética , Monoacilglicerol Lipasas/genética , Mutación , Adulto , Niño , Adolescente , GenotipoRESUMEN
Hereditary transthyretin-mediated amyloidosis (ATTRv amyloidosis), known as Corino de Andrade disease, is a rare neurodegenerative disorder with a significant global impact characterized by the misfolding of transthyretin (TTR) protein leading to amyloid aggregation, ATTRv amyloidosis, especially with polyneuropathy, poses a considerable challenge in managing its rapid progression and debilitating effects. This mini-review focuses on the recent advancements in the treatment landscape for ATTRv amyloidosis with polyneuropathy, specifically the RNA interference therapeutic Vutrisiran and the ligand-conjugated antisense oligonucleotide Eplontersen. We aim to provide a comprehensive overview of the mechanisms, current evidence from clinical trials, and future directions for these novel therapeutic agents. Vutrisiran and Eplontersen have demonstrated significant clinical efficacy in improving neuropathic impairment, quality of life, and serum TTR levels in various trials. The distinct mechanistic approaches of these therapies, coupled with their acceptable safety profiles, offer promising avenues for addressing the complexities of ATTRv amyloidosis with polyneuropathy. The introduction of Vutrisiran and Eplontersen marks a pivotal moment in the quest for effective therapies against ATTRv amyloidosis with polyneuropathy. While clinical evidence is promising, ongoing research is crucial to deepen mechanistic understanding and address research gaps. Future perspectives include the potential expansion of therapeutic options and a more inclusive approach to cater to the diverse needs of individuals globally. This mini-review provides valuable insights into the evolving landscape of ATTRv amyloidosis management and sets the stage for further exploration in this challenging domain.
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Neuropatías Amiloides Familiares , Polineuropatías , Humanos , Neuropatías Amiloides Familiares/genética , Neuropatías Amiloides Familiares/terapia , Polineuropatías/genética , Oligonucleótidos/uso terapéutico , Oligonucleótidos Antisentido/uso terapéutico , Prealbúmina/genética , Calidad de VidaRESUMEN
Hereditary transthyretin amyloidosis (hATTR) with polyneuropathy (formerly known as Familial Amyloid Polyneuropathy (FAP)) is an endemic amyloidosis involving the harmful aggregation of proteins, most commonly transthyretin (TTR) but sometimes also apolipoprotein A-1 or gelsolin. hATTR appears to be transmitted as an autosomal dominant trait. Over 100 point mutations have been identified, with the Val30Met substitution being the most common. Yet, the mechanism of pathogenesis and the overall origin of hATTR remain unclear. Here, we argue that hATTR could be related to harmful metal exposure. hATTR incidence is unevenly distributed globally, and the three largest defined clusters exist in Japan, Portugal, and Sweden. All three disease regions are also ancient mining districts with associated metal contamination of the local environment. There are two main mechanisms for how harmful metals, after uptake into tissues and body fluids, could induce hATTR. First, the metals could directly influence the expression, function, and/or aggregation of the proteins involved in hATTR pathology. Such metal-protein interactions might constitute molecular targets for anti-hATTR drug design. Second, metal exposure could induce hATTR -associated genetic mutations, which may have happened several generations ago. These two mechanisms can occur in parallel. In conclusion, the possibility that hATTR could be related to metal exposure in geochemically defined regions deserves further attention.
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Neuropatías Amiloides Familiares , Prealbúmina , Humanos , Neuropatías Amiloides Familiares/genética , Neuropatías Amiloides Familiares/epidemiología , Prealbúmina/genética , Prealbúmina/metabolismo , Minería , Polineuropatías/genética , Polineuropatías/epidemiología , Polineuropatías/etiología , Portugal/epidemiologíaRESUMEN
BACKGROUND AND AIMS: To further substantiate the role of antibody-mediated complement activation in multifocal motor neuropathy (MMN) immunopathology, we investigated the distribution of promotor polymorphisms of genes encoding the membrane-bound complement regulators CD46, CD55, and CD59 in patients with MMN and controls, and evaluated their association with disease course. METHODS: We used Sanger sequencing to genotype five common polymorphisms in the promotor regions of CD46, CD55, and CD59 in 133 patients with MMN and 380 controls. We correlated each polymorphism to clinical parameters. RESULTS: The genotype frequencies of rs28371582, a 21-bp deletion in the CD55 promotor region, were altered in patients with MMN as compared to controls (p .009; Del/Del genotype 16.8% vs. 7.7%, p .005, odds ratio: 2.43 [1.27-4.58]), and patients carrying this deletion had a more favorable disease course (mean difference 0.26 Medical Research Council [MRC] points/year; 95% confidence interval [CI]: 0.040-0.490, p .019). The presence of CD59 rs141385724 was associated with less severe pre-diagnostic disease course (mean difference 0.940 MRC point/year; 95% CI: 0.083-1.80, p .032). INTERPRETATION: MMN susceptibility is associated with a 21-bp deletion in the CD55 promotor region (rs2871582), which is associated with lower CD55 expression. Patients carrying this deletion may have a more favorable long-term disease outcome. Taken together, these results point out the relevance of the pre-C5 level of the complement cascade in the inflammatory processes underlying MMN.
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Antígenos CD55 , Regiones Promotoras Genéticas , Humanos , Antígenos CD55/genética , Masculino , Femenino , Persona de Mediana Edad , Anciano , Adulto , Proteína Cofactora de Membrana/genética , Antígenos CD59/genética , Eliminación de Secuencia , Polineuropatías/genética , Polineuropatías/fisiopatología , Polineuropatías/inmunología , Progresión de la Enfermedad , GenotipoRESUMEN
OBJECTIVE: To evaluate serum neurofilament light chain (sNfL) as biomarker of disease onset, progression and treatment effect in hereditary transthyretin (ATTRv) amyloidosis patients and TTR variant (TTRv) carriers. METHODS: sNfL levels were assessed longitudinally in persistently asymptomatic TTRv carriers (N = 12), persistently asymptomatic ATTRv amyloidosis patients (defined as asymptomatic patients but with amyloid detectable in subcutaneous abdominal fat tissue) (N = 8), in TTRv carriers who developed polyneuropathy (N = 7) and in ATTRv amyloidosis patients with polyneuropathy on treatment (TTR-stabiliser (N = 20) or TTR-silencer (N = 18)). Polyneuropathy was confirmed by nerve conduction studies or quantitative sensory testing. sNfL was analysed using a single-molecule array assay. RESULTS: sNfL increased over 2 years in persistently asymptomatic ATTRv amyloidosis patients, but did not change in persistently asymptomatic TTRv carriers. In all TTRv carriers who developed polyneuropathy, sNfL increased from 8.4 to 49.8 pg/mL before the onset of symptoms and before polyneuropathy could be confirmed neurophysiologically. In symptomatic ATTRv amyloidosis patients on a TTR-stabiliser, sNfL remained stable over 2 years. In patients on a TTR-silencer, sNfL decreased after 1 year of treatment. CONCLUSION: sNfL is a biomarker of early neuronal damage in ATTRv amyloidosis already before the onset of polyneuropathy. Current data support the use of sNfL in screening asymptomatic TTRv carriers and in monitoring of disease progression and treatment effect.
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Neuropatías Amiloides Familiares , Biomarcadores , Proteínas de Neurofilamentos , Prealbúmina , Humanos , Neuropatías Amiloides Familiares/sangre , Neuropatías Amiloides Familiares/genética , Neuropatías Amiloides Familiares/patología , Proteínas de Neurofilamentos/sangre , Masculino , Femenino , Persona de Mediana Edad , Biomarcadores/sangre , Anciano , Prealbúmina/genética , Prealbúmina/metabolismo , Estudios Longitudinales , Adulto , Polineuropatías/sangre , Polineuropatías/genética , Polineuropatías/patología , Polineuropatías/diagnóstico , Neuronas/metabolismo , Neuronas/patologíaRESUMEN
BACKGROUND: PHARC syndrome (MIM:612674) is a rare neurodegenerative disorder characterized by demyelinating polyneuropathy, hearing loss, ataxia, retinitis pigmentosa, and cataracts (PHARC). The syndrome is caused by mutations in the ABHD12 gene, which encodes αß-hydrolase domain-containing protein 12 related to endocannabinoid metabolism. PHARC syndrome is one of the rare diseases; so far, only 51 patients have been reported in the literature. METHODS: We evaluated the 25-year-old male patient referred to us due to vision loss, cataracts, and hearing loss. Ophthalmological examinations and genetic analyses were performed using targeted next-generation sequencing. RESULTS: In the genetic analysis, the patient was diagnosed with PHARC syndrome by detecting homozygous (NM_001042472.3): c.871del (p.Tyr291IlefsTer28) novel pathogenic variation in the ABHD12 gene. Following the molecular diagnosis, he was referred to the neurology department for reverse phenotyping and sensorimotor demyelinating polyneuropathy was detected in the neurological evaluation. CONCLUSIONS: In this study, we report a novel variation in ABHD12 gene in the first Turkish-origin PHARC patient. We present this study to contribute genotype-phenotype correlation of PHARC syndrome and emphasize the importance of molecular genetic diagnosis in order to determine the appropriate clinical approach. This report is essential for expanding the phenotypic spectrum in different populations and understanding the genotype-phenotype correlation of PHARC syndrome via novel pathogenic variation in the ABHD12 gene.
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Ataxia , Catarata , Pérdida Auditiva , Polineuropatías , Retinitis Pigmentosa , Masculino , Humanos , Adulto , Fenotipo , Retinitis Pigmentosa/diagnóstico , Retinitis Pigmentosa/genética , Retinitis Pigmentosa/patología , Mutación , Síndrome , Catarata/diagnóstico , Catarata/genética , Polineuropatías/diagnóstico , Polineuropatías/genética , Polineuropatías/patología , Linaje , Monoacilglicerol Lipasas/genéticaRESUMEN
BACKGROUND: Hereditary transthyretin amyloidosis (ATTRv) is an adult-onset autosomal dominant disease resulting from TTR gene pathogenic variants. ATTRv often presents as a progressive polyneuropathy, and effective ATTRv treatments are available. METHODS: In this 5 year-long (2017-2021) nationwide prospective study, we systematically analysed the TTR gene in French patients with age >50 years with a progressive idiopathic polyneuropathy. RESULTS: 553 patients (70% males) with a mean age of 70 years were included. A TTR gene pathogenic variant was found in 15 patients (2.7%), including the Val30Met TTR variation in 10 cases. In comparison with patients with no TTR gene pathogenic variants (n = 538), patients with TTR pathogenic variants more often presented with orthostatic hypotension (53 vs. 21%, p = .007), significant weight loss (33 vs 11%, p = .024) and rapidly deteriorating nerve conduction studies (26 vs. 8%, p = .03). ATTRv diagnosis led to amyloid cardiomyopathy diagnosis in 11 cases, ATTRv specific treatment in all cases and identification of 15 additional ATTRv cases among relatives. CONCLUSION: In this nationwide prospective study, we found ATTRv in 2.7% of patients with age >50 years with a progressive polyneuropathy. These results are highly important for the early identification of patients in need of disease-modifying treatments.
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Neuropatías Amiloides Familiares , Polineuropatías , Masculino , Adulto , Persona de Mediana Edad , Anciano , Humanos , Femenino , Estudios Prospectivos , Neuropatías Amiloides Familiares/patología , Polineuropatías/diagnóstico , Polineuropatías/genética , Resultado del Tratamiento , Prealbúmina/genéticaRESUMEN
Tatton-Brown-Rahman syndrome (TBRS) is a rare autosomal dominant overgrowth syndrome first reported in 2014 and caused by pathogenic variants in the DNA methyltransferase 3A (DNMT3A) gene. All individuals reported to date share a phenotype of somatic overgrowth, dysmorphic features, and intellectual disability. Peripheral neuropathy was not described in these cases. We report an adult patient with TBRS caused by a novel pathogenic DNMT3A variant (NM_175629.2: c.2036G>A, p.(Arg688His)) harboring an axonal length-dependent sensory-motor polyneuropathy. Extensive laboratory and molecular genetic work-up failed to identify alternative causes for this patient's neuropathy. We propose that axonal neuropathy may be a novel, age-dependent phenotypic feature in adults with TBRS and suggest that this syndrome should be considered in the differential diagnosis of patients with overgrowth, cognitive and psychiatric difficulties, and peripheral neuropathy.
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Anomalías Múltiples , Discapacidad Intelectual , Anomalías Musculoesqueléticas , Polineuropatías , Adulto , Humanos , ADN Metiltransferasa 3A , Discapacidad Intelectual/diagnóstico , Discapacidad Intelectual/genética , ADN (Citosina-5-)-Metiltransferasas/genética , Mutación , Anomalías Múltiples/genética , Síndrome , Polineuropatías/diagnóstico , Polineuropatías/genéticaAsunto(s)
Polineuropatías , Hermanos , Humanos , Polineuropatías/genética , Mutación/genética , Conducción Nerviosa/genéticaRESUMEN
BACKGROUND AND PURPOSE: Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) is caused by mutations in the TTR gene, leading to misfolded monomers that aggregate generating amyloid fibrils. METHODS: A prospective systematic genetic screening for ATTRv-PN was proposed in patients presenting with a sensory-motor idiopathic polyneuropathy and two or more "red flags" among the following: family history of polyneuropathy or cardiopathy, bilateral carpal tunnel syndrome, cardiac insufficiency, renal amyloidosis, lumbar tract stenosis, autonomic dysfunction, idiopathic gastrointestinal disease, amyloid deposits on biopsy, and vitreous opacities. The detection rate was calculated, and nonparametric analyses were carried out to underline differences among screened positive versus negative patients. RESULTS: In the first step, 145 suspected patients underwent genetic testing, revealing a diagnosis of ATTRv-PN in 14 patients (10%). Then, cascade screening allowed early recognition of 33 additional individuals (seven symptomatic ATTRv-PN patients and 26 presymptomatic carriers) among 84 first-degree relatives. Patients with a positive genetic test presented a higher frequency of unexplained weight loss, gastrointestinal symptoms, and family history of cardiopathy. CONCLUSIONS: A systematic screening for ATTRv-PN yielded an increased recognition of the disease in our neurological clinic. Unexplained weight loss associated with axonal polyneuropathy had the highest predictive value in the guidance of clinical suspicion. A focused approach for the screening of ATTRv-PN could lead to an earlier diagnosis and identification of asymptomatic carriers, who will be promptly treated after a strict follow-up at the clinical onset.
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Neuropatías Amiloides Familiares , Polineuropatías , Humanos , Estudios Prospectivos , Sicilia , Neuropatías Amiloides Familiares/complicaciones , Neuropatías Amiloides Familiares/diagnóstico , Neuropatías Amiloides Familiares/genética , Polineuropatías/diagnóstico , Polineuropatías/genética , Pruebas Genéticas , Pérdida de PesoRESUMEN
Hereditary transthyretin amyloidosis with polyneuropathy (ATTR-PN) results from specific TTR gene mutations. In this study, we generated two induced pluripotent stem cell (iPSC) lines derived from ATTR-PN patients with heterozygous TTR gene mutations (Ala97Ser and Phe64Leu). These iPSC lines exhibited normal morphology, karyotype, high pluripotency marker expression, and differentiation into cells representing all germ layers. The generation of these iPSC lines serve as a valuable tool for investigating the mechanisms of ATTR-PN across various cell types and facilitating patient-specific in vitro amyloidosis modeling.
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Neuropatías Amiloides Familiares , Células Madre Pluripotentes Inducidas , Polineuropatías , Humanos , Células Madre Pluripotentes Inducidas/metabolismo , Prealbúmina/genética , Prealbúmina/metabolismo , Neuropatías Amiloides Familiares/genética , Neuropatías Amiloides Familiares/metabolismo , Polineuropatías/genética , Polineuropatías/metabolismo , Mutación/genéticaRESUMEN
BACKGROUND AND AIMS: POLR3B gene encodes a subunit of RNA polymerase III (Pol III). Biallelic mutations in POLR3B are associated with leukodystrophies, but recently de novo heterozygous mutations have been described in early onset peripheral demyelinating neuropathies with or without central involvement. Here, we report the first Italian case carrying a de novo variant in POLR3B with a pure neuropathy phenotype and primary axonal involvement of the largest nerve fibers. METHODS: Nerve conduction studies, sympathetic skin response, dynamic sweat test, tactile and thermal quantitative sensory testing and brain magnetic resonance imaging were performed according to standard procedures. Histopathological examination was performed on skin and sural nerve biopsies. Molecular analysis of the proband and his relatives was performed with Next Generation Sequencing. The impact of the identified variant on the overall protein structure was evaluated through rotamers method. RESULTS: Since his early adolescence, the patient presented with signs of polyneuropathy with severe distal weakness, atrophy, and reduced sensation. Neurophysiological studies showed a sensory-motor axonal polyneuropathy, with confirmed small fiber involvement. In addition, skin biopsy and sural nerve biopsy showed predominant large fibers involvement. A trio's whole exome sequencing revealed a novel de novo variant p.(Arg1046Cys) in POLR3B, which was classified as Probably Pathogenic. Molecular modeling data confirmed a deleterious effect of the variant on protein structure. INTERPRETATION: Neurophysiological and morphological findings suggest a primary axonal involvement of the largest nerve fibers in POLR3B-related neuropathies. A partial loss of function mechanism is proposed for both neuropathy and leukodystrophy phenotypes.
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Enfermedades Desmielinizantes , Enfermedades del Sistema Nervioso Periférico , Polineuropatías , ARN Polimerasa III , Adolescente , Humanos , Axones , Enfermedades Desmielinizantes/genética , Mutación , Fibras Nerviosas/metabolismo , Enfermedades del Sistema Nervioso Periférico/genética , Polineuropatías/genética , Proteínas/genética , ARN Polimerasa III/genética , ARN Polimerasa III/metabolismoRESUMEN
Silencing the transthyretin (TTR) gene is an effective strategy in the treatment of hereditary transthyretin-mediated (hATTR) amyloidosis. Vutrisiran (Amvuttra®), an RNA interference (RNAi) therapeutic targeting TTR mRNA, is approved in the USA and EU for the treatment of adults with polyneuropathy of hATTR amyloidosis. N-acetylgalactosamine conjugation and enhanced stabilisation chemistry are utilised to target vutrisiran to the liver and increase stability, respectively, allowing for subcutaneous administration once every 3 months. In a pivotal phase 3 study in patients with hATTR amyloidosis with polyneuropathy, subcutaneous vutrisiran 25 mg every 3 months significantly reduced neuropathy impairment versus external placebo. Vutrisiran was also associated with significant improvements in neuropathy-specific quality of life, gait speed, nutritional status and disability scores. Vutrisiran was generally well tolerated; the only common adverse events to occur at a greater incidence than with external placebo were pain in extremity and arthralgia. Vutrisiran reduces serum vitamin A levels and vitamin A supplementation is recommended. In conclusion, vutrisiran is an efficacious and generally well-tolerated alternative option for the treatment of polyneuropathy of hATTR amyloidosis, which has the potential advantage of infrequent subcutaneous dosage.
Hereditary transthyretin-mediated (hATTR) amyloidosis is a progressive and disabling disease caused by variants in the transthyretin (TTR) gene, which cause destabilisation and misfolding of the TTR protein. Deposition of misfolded TTR protein (amyloid) around nerves causes a range of neuropathic symptoms. Vutrisiran (Amvuttra®) silences the TTR gene via RNA interference (RNAi). Vutrisiran, administered subcutaneously once every 3 months, is approved in the USA and EU for the treatment of polyneuropathy of hATTR amyloidosis in adults. In a phase 3 study in patients with hATTR amyloidosis with polyneuropathy, vutrisiran significantly reduced neuropathy impairment and improved other disease-related outcomes versus external placebo. Vutrisiran was generally well tolerated, with most adverse events being mild or moderate in severity. As vutrisiran decreases vitamin A levels, patients undergoing vutrisiran treatment should supplement with vitamin A. In conclusion, vutrisiran is an efficacious and generally well-tolerated alternative option for the treatment of polyneuropathy of hATTR amyloidosis, with a convenient dosage regimen.
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Neuropatías Amiloides Familiares , Polineuropatías , Adulto , Humanos , Calidad de Vida , Prealbúmina/genética , Vitamina A/uso terapéutico , Neuropatías Amiloides Familiares/tratamiento farmacológico , Neuropatías Amiloides Familiares/genética , Polineuropatías/tratamiento farmacológico , Polineuropatías/genéticaRESUMEN
Congenital hypomyelinating polyneuropathy (HPN) restricted to the peripheral nervous system was reported in 1989 in two Golden Retriever (GR) littermates. Recently, four additional cases of congenital HPN in young, unrelated GRs were diagnosed via neurological examination, electrodiagnostic evaluation, and peripheral nerve pathology. Whole-genome sequencing was performed on all four GRs, and variants from each dog were compared to variants found across >1,000 other dogs, all presumably unaffected with HPN. Likely causative variants were identified for each HPN-affected GR. Two cases shared a homozygous splice donor site variant in MTMR2, with a stop codon introduced within six codons following the inclusion of the intron. One case had a heterozygous MPZ isoleucine to threonine substitution. The last case had a homozygous SH3TC2 nonsense variant predicted to truncate approximately one-half of the protein. Haplotype analysis using 524 GR established the novelty of the identified variants. Each variant occurs within genes that are associated with the human Charcot-Marie-Tooth (CMT) group of heterogeneous diseases, affecting the peripheral nervous system. Testing a large GR population (n = >200) did not identify any dogs with these variants. Although these variants are rare within the general GR population, breeders should be cautious to avoid propagating these alleles.
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Enfermedad de Charcot-Marie-Tooth , Polineuropatías , Humanos , Animales , Perros , Enfermedad de Charcot-Marie-Tooth/genética , Enfermedad de Charcot-Marie-Tooth/veterinaria , Enfermedad de Charcot-Marie-Tooth/patología , Proteínas/genética , Heterocigoto , Polineuropatías/genética , Polineuropatías/veterinaria , Alelos , Mutación , Proteínas Tirosina Fosfatasas no Receptoras/genética , Péptidos y Proteínas de Señalización Intracelular/genética , Proteína P0 de la Mielina/genéticaRESUMEN
BACKGROUND: Early diagnosis of hereditary ATTR polyneuropathy (ATTRv-PN) is important since treatment options have become available, which are most effective early in the disease course. ATTRv-PN is likely underdiagnosed as patients might be misdiagnosed with idiopathic polyneuropathy. It is uncertain if it is useful to test for TTR gene mutations in patients with a typical presentation for chronic idiopathic axonal polyneuropathy (CIAP) and which are the distinguishing clinical features. METHODS: We carried out a retrospective cohort study to assess the yield of TTR gene sequencing in patients with polyneuropathy and assessed if the identified patients with ATTRv-PN had a clinical presentation typical of CIAP. Additionally, we assessed which clinical features, including previously defined red flag symptoms, can differentiate between patients with CIAP and ATTRv-PN and assessed the performance of the TTR suspicion index. RESULTS: Out of 338 patients with polyneuropathy, 10 patients had a pathogenic TTR gene mutation (all p.Val50Met) and none had a clinical presentation typical of CIAP. Patients with ATTRv-PN more often had bilateral CTS, motor involvement of arms, cardiac involvement, family history suggestive of hATTRv, and autonomic symptoms than patients with CIAP. All patients with ATTRv-PN as well as 70% of patients with CIAP fulfilled the suspicion index. CONCLUSION: Routine TTR gene sequencing in patients with a typical presentation for CIAP is not useful. However, red flag symptoms can differentiate patients with ATTRv-PN from patients with CIAP. We propose an adjusted version of the TTR suspicion index to increase diagnostic yield.
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Neuropatías Amiloides Familiares , Polineuropatías , Humanos , Neuropatías Amiloides Familiares/diagnóstico , Neuropatías Amiloides Familiares/genética , Prealbúmina/genética , Estudios Retrospectivos , Polineuropatías/diagnóstico , Polineuropatías/genética , Progresión de la EnfermedadRESUMEN
OBJECTIVE: Hereditary amyloid transthyretin (ATTRv) amyloidosis with polyneuropathy, a rare autosomal-dominant disease, has gained attention in recent years owing to treatment improvements. However, epidemiological real-world mega database of nationwide natural history and survival rates, especially with the specific mutation of Ala97Ser, are limited. METHODS: Taiwan National Health Insurance Research Database contains data from over 23 million individuals; Among them, 175 ATTRv amyloidosis patients validated by rare disease registry were enrolled. Multivariable Cox proportional hazard analyses were applied to investigate the association between baseline characteristics and all-cause mortality. FINDINGS: From 2008 to 2020, the annual incidence and prevalence rates of specific mutations (Ala97Ser) leading to ATTRv amyloidosis with polyneuropathy were 0.04-1.14 and 0.04-4.79 per million in Taiwan, respectively. In Taiwan, these patients exhibited male predominance with a mean age at validation of 62.75 years. At the 5th year after validation, patients exhibited a survival rate of approximately 50%, with higher mortality in male patients (hazard ratio [HR]: 2.22, 95% confidence interval [CI]: 1.15-4.31) and patients older at validation (HR: 1.10, 95% CI: 1.06-1.15). The two most common departments in outpatient were neurology and family medicine, and neurology and cardiology in inpatient. The three most common causes of death registered were unspecified amyloidosis (30.6%), organ-limited amyloidosis (20.9%), and neuropathic heredofamilial amyloidosis (9.7%). INTERPRETATION: The annual prevalence rate of specific mutation (Ala97Ser)-dominant ATTRv amyloidosis with polyneuropathy in Taiwan is comparable to the mid- to high-prevalence country level of the research by Schmidt et al. The extraordinarily high mortality, especially among patients older at validation, may reflect the inadequate awareness and the necessity of early intervention with novel disease-modifying regimens.
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Neuropatías Amiloides Familiares , Amiloidosis Familiar , Polineuropatías , Humanos , Masculino , Persona de Mediana Edad , Femenino , Tasa de Supervivencia , Neuropatías Amiloides Familiares/epidemiología , Neuropatías Amiloides Familiares/genética , Polineuropatías/epidemiología , Polineuropatías/genética , MutaciónAsunto(s)
Neuropatías Amiloides Familiares , Polineuropatías , Humanos , Neuropatías Amiloides Familiares/diagnóstico , Neuropatías Amiloides Familiares/genética , Prealbúmina/genética , Polineuropatías/diagnóstico , Polineuropatías/genética , Mutación , Pruebas Genéticas , Errores Diagnósticos , Amiloide/genética , Amiloide/metabolismoRESUMEN
INTRODUCTION: NAGLU encodes N-acetyl-alpha-glucosaminidase, an enzyme that degrades heparan sulfate. Biallelic NAGLU mutations cause mucopolysaccharidosis IIIB, a severe childhood-onset neurodegenerative disease, while monoallelic mutations are associated to late-onset, dominantly inherited painful sensory neuropathy. However, to date, only one family with a dominant NAGLU-related neuropathy has been described. CASE REPORT: Here we describe a patient with early-onset motor polyneuropathy harboring a novel monoallelic NAGLU mutation. We found reduced NAGLU enzymatic activity thus corroborating the pathogenic role of the new variant. DISCUSSION: Our report represents the second ever described case with dominant NAGLU-related neuropathy and the first case with early-onset motor symptoms. We underlie the importance of a thorough clinical description of this probably underestimated new clinical entity.
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Neuropatías Hereditarias Sensoriales y Autónomas , Mucopolisacaridosis III , Enfermedades Neurodegenerativas , Enfermedades del Sistema Nervioso Periférico , Polineuropatías , Humanos , Niño , Mucopolisacaridosis III/diagnóstico , Mucopolisacaridosis III/genética , Mucopolisacaridosis III/patología , Polineuropatías/genética , Mutación/genéticaRESUMEN
BACKGROUND: The role of biallelic variants in the NRCAM gene underlying a neurodevelopmental disorder has been defined recently. The phenotype is mainly recognized by varying severity of global developmental delay/intellectual disability, hypotonia, spasticity, and peripheral neuropathy. METHODS: Here, we describe a patient with an initial diagnosis of motor-predominant axonal polyneuropathy or a form of distal SMA. Whole-exome sequencing (WES), in parallel with WES-based CNV detection and assessment of homozygosity runs, was performed to identify this patient's possible genetic cause. RESULTS: Whole exome sequencing revealed a homozygous variant, c.73C > T (p.Gln25*), in the NRCAM gene, while the patient manifests a mild range of phenotypes compared to NRCAM-related disorder. He presented only motor-predominant axonal polyneuropathy with no other signs of central nervous system involvement. CONCLUSIONS: This study is the second report of an association between biallelic NRCAM gene variants and a Mendelian disorder. The obtained clinical data, together with the molecular findings in this patient, expands the clinical and molecular spectrum of NRCAM-related disorder and highlights its phenotypic complexity. Although patients with loss of function variants in this gene have previously presented severe clinical features, we show that type of the pathogenic variant does not necessarily determine the severity of this phenotype.
Asunto(s)
Discapacidad Intelectual , Trastornos del Neurodesarrollo , Polineuropatías , Masculino , Humanos , Trastornos del Neurodesarrollo/genética , Discapacidad Intelectual/genética , Fenotipo , Pérdida de Heterocigocidad , Polineuropatías/genética , Moléculas de Adhesión Celular/genéticaRESUMEN
BACKGROUND: TTR aggregation causes hereditary transthyretin (TTR) polyneuropathy (ATTRv-PN) in individuals with destabilised TTR variants. ATTRv-PN can be treated with ligands that bind TTR and prevent aggregation. One such ligand, tafamidis, is widely approved to treat ATTRv-PN. We explore how TTR stabilisation markers relate to clinical efficacy in 210 ATTRv-PN patients taking tafamidis. METHODS: TTR concentration in patient plasma was measured before and after tafamidis treatment using assays for native or combined native + non-native TTR. TTR tetramer dissociation kinetics, which are slowed by tafamidis binding, were also measured. RESULTS: Native TTR levels increased by 56.8% while combined native + non-native TTR levels increased by 3.1% after 24 months of tafamidis treatment, implying that non-native TTR decreased. Accordingly, the fraction of native TTR increased from 0.54 to 0.71 with tafamidis administration. Changes in native and non-native TTR levels were uncorrelated with clinical response to tafamidis. TTR tetramer dissociation generally slowed to an extent consistent with â¼40% of TTR being tafamidis-bound. Male non-responders had a lower extent of binding. CONCLUSIONS: Native and non-native TTR concentration changes cannot be used as surrogate measures for therapeutic efficacy. Also, successful tafamidis therapy requires only moderate TTR stabilisation. Male patients may benefit from higher tafamidis doses.