Clinicopathological Features of Amyloid Neuropathy: A Four Decade Experience.

BACKGROUND: Peripheral neuropathy is one of the manifestations of primary or familial amyloidosis. Published studies from India are limited. MATERIALS AND METHODS: We reviewed the clinical and pathological features of amyloid neuropathy diagnosed at our Institute over the last 39 years. RESULTS: Fifty-five cases of amyloid neuropathies were diagnosed between 1981 and 2019, constituting 0.28% of peripheral nerve biopsies (55/19,081). Age at presentation ranged from 24 to 81 years (mean-48 years) with male preponderance [M:F = 3.58:1]. Duration of symptoms at presentation varied from 3 months to 10 years (mean-2.31 years). Majority presented with small fiber neuropathy (85%). Pure sensory symptoms predominated in 23%, while 72% had sensorimotor neuropathy and 35.8% had autonomic involvement, with isolated autonomic failure in one patient. Amyloid neuropathy was clinically suspected in 22.6% of nonfamilial cases. Familial amyloid neuropathy was suspected in eight patients. Genetic testing detected ATTR and gelsolin mutation in one each of tested patients. Nerve biopsies revealed characteristic birefringent amyloid deposits stained mahogany brown by Congo red predominantly surrounding endoneurial microvessels (34.5%), also in perineurium and epineurium in 25.45% cases. Preferential loss of small diameter myelinated fibers was noted. Axonal degeneration or regeneration was conspicuously absent. CONCLUSION: Amyloid neuropathy is uncommon (0.28% of nerve biopsies in our series). Nerve biopsy is essential for the diagnosis. We report our experience of amyloid neuropathy and underscore the importance of making an assiduous search for amyloid deposits in the appropriate setting. Awareness of this entity is important for early diagnosis in the light of emerging therapeutic advances.

Amyloid Neuropathy: From Pathophysiology to Treatment in Light-Chain Amyloidosis and Hereditary Transthyretin Amyloidosis.

Amyloid neuropathy is caused by deposition of insoluble ß-pleated amyloid sheets in the peripheral nervous system. It is most common in: (1) light-chain amyloidosis, a clonal non-proliferative plasma cell disorder in which fragments of immunoglobulin, light or heavy chain, deposit in tissues, and (2) hereditary transthyretin (ATTRv) amyloidosis, a disorder caused by autosomal dominant mutations in the TTR gene resulting in mutated protein that has a higher tendency to misfold. Amyloid fibrils deposit in the endoneurium of peripheral nerves, often extensive in the dorsal root ganglia and sympathetic ganglia, leading to atrophy of Schwann cells in proximity to amyloid fibrils and blood-nerve barrier disruption. Clinically, amyloid neuropathy is manifested as a length-dependent sensory predominant neuropathy associated with generalized autonomic failure. Small unmyelinated nerves are involved early and prominently in early-onset Val30Met ATTRv, whereas other ATTRv and light-chain amyloidosis often present with large- and small-fiber involvement. Nerve conduction studies, quantitative sudomotor axon testing, and intraepidermal nerve fiber density are useful tools to evaluate denervation. Amyloid deposition can be demonstrated by tissue biopsy of the affected organ or surrogate site, as well as bone-avid radiotracer cardiac imaging. Treatment of light-chain amyloidosis has been revolutionized by monoclonal antibodies and stem cell transplantation with improved 5-year survival up to 77%. Novel gene therapy and transthyretin stabilizers have revolutionized treatment of ATTRv, improving the course of neuropathy (less change in the modified Neuropathy Impairment Score + 7 from baseline) and quality of life. With great progress in amyloidosis therapies, early diagnosis and presymptomatic testing for ATTRv family members has become paramount. ANN NEUROL 2024;96:423-440.

Mimicking kidney flow shear efficiently induces aggregation of LECT2, a protein involved in renal amyloidosis.

Aggregation of leukocyte cell-derived chemotaxin 2 (LECT2) causes ALECT2, a systemic amyloidosis that affects the kidney and liver. Previous studies established that LECT2 fibrillogenesis is accelerated by the loss of its bound zinc ion and stirring/shaking. These forms of agitation create heterogeneous shear conditions, including air-liquid interfaces that denature proteins, that are not present in the body. Here, we determined the extent to which a more physiological form of mechanical stress-shear generated by fluid flow through a network of narrow channels-drives LECT2 fibrillogenesis. To mimic blood flow through the kidney, where LECT2 and other proteins form amyloid deposits, we developed a microfluidic device consisting of progressively branched channels narrowing from 5 mm to 20 µm in width. Shear was particularly pronounced at the branch points and in the smallest capillaries. Aggregation was induced within 24 h by shear levels that were in the physiological range and well below those required to unfold globular proteins such as LECT2. EM images suggested the resulting fibril ultrastructures were different when generated by laminar flow shear versus shaking/stirring. Importantly, results from the microfluidic device showed the first evidence that the I40V mutation accelerated fibril formation and increased both the size and the density of the aggregates. These findings suggest that kidney-like flow shear, in combination with zinc loss, acts in combination with the I40V mutation to trigger LECT2 amyloidogenesis. These microfluidic devices may be of general use for uncovering mechanisms by which blood flow induces misfolding and amyloidosis of circulating proteins.

Vutrisiran: a new drug in the treatment landscape of hereditary transthyretin amyloid polyneuropathy.

INTRODUCTION: Hereditary transthyretin (ATTRv) amyloidosis is a progressive, fatal disorder caused by mutations in the transthyretin (TTR) gene leading to deposition of the misfolded protein in amyloid fibrils. The main phenotypes are peripheral neuropathy (PN) and cardiomyopathy (CM). AREAS COVERED: Gene silencing therapy, by dramatically reducing liver production of TTR, has transformed ATTRv-PN patient care in the last decade. In this drug discovery case history, the authors discuss the treatment history of ATTRv-PN and focus on the latest siRNA therapy: vutrisiran. Vutrisiran is chemically enhanced and N-acetylgalactosamin-conjugated, allowing increased stability and specific liver delivery. HELIOS-A, a phase III, multicenter randomized study, tested vutrisiran in ATTRv-PN and showed significant improvement in neuropathy impairment, disability, quality of life (QoL), gait speed, and nutritional status. Tolerance was acceptable, no safety signals were raised. EXPERT OPINION: Vutrisiran offers a new treatment option for patients with ATTRv-PN. Vutrisian's easier delivery and administration route, at a quarterly frequency, as well as the absence of premedication, are major improvements to reduce patients' disease burden and improve their QoL. Its place in the therapeutic strategy is to be determined, considering affordability.

Disease-Modifying Drugs Extend Survival in Hereditary Transthyretin Amyloid Polyneuropathy.

Hereditary transthyretin (ATTRv) amyloidosis is a rare, fatal systemic disease, associated with polyneuropathy and cardiomyopathy, that is caused by mutant transthyretin (TTR). In addition to liver transplantation, several groundbreaking disease-modifying drugs (DMDs) such as tetrameric TTR stabilizers and TTR gene-silencing therapies have been developed for ATTRv amyloid polyneuropathy. They were based on a working hypothesis of the mechanisms of ATTRv amyloid formation. In this retrospective cohort study, we investigated survival of all 201 consecutive patients with ATTRv amyloidosis in our center. The effects of DMDs on survival improvements were significant not only in early-onset patients but also in late-onset patients. ANN NEUROL 2024;95:230-236.

Hereditary transthyretin amyloid neuropathies: advances in pathophysiology, biomarkers, and treatment.

Hereditary transthyretin (TTR) amyloid polyneuropathy is an autosomal dominant life-threatening disorder. TTR is produced mainly by the liver but also by the choroid plexus and retinal pigment epithelium. Detailed clinical characterisation, identification of clinical red flags for misdiagnosis, and use of biomarkers enable early diagnosis and treatment. In addition to liver transplantation and TTR stabilisers, three other disease-modifying therapies have regulatory approval: one antisense oligonucleotide (inotersen) and two small interfering RNAs (siRNAs; patisiran and vutrisiran). The siRNAs have been shown to stop progression of neuropathy and improve patients' quality of life. As none of the disease-modifying therapies can cross the blood-brain barrier, TTR deposition in the CNS, which can cause stroke and cognitive impairment, remains an important unaddressed issue. CRISPR-Cas9-based one-time TTR editing therapy is being investigated in a phase 1 clinical study. Identification of the earliest stages of pathogenesis in TTR variant carriers is a major challenge that needs addressing for optimal management.

Cardiomyopathy correlates to nerve damage in p.A117S late-onset transthyretin amyloid polyneuropathy.

OBJECTIVE: Late-onset hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) is often associated with heart involvement. Recent advances in cardiac imaging allow the detection of cardiac amyloidosis. This study aimed to explore cardiomyopathy by cardiac imaging and its clinical correlates with polyneuropathy in late-onset ATTRv-PN. METHODS: Polyneuropathy was assessed by intraepidermal nerve fiber (IENF) density, nerve conduction study (NCS), autonomic function tests, quantitative sensory testing, and clinical questionnaires. Cardiomyopathy was evaluated by echocardiography, 99m Tc-pyrophosphate (PYP) single-photon emission computed tomography (SPECT) imaging, cardiac magnetic resonance imaging (CMR), and serum Pro-B-type natriuretic peptide. Healthy controls and patients with Brugada syndrome were enrolled for comparison of CMR. RESULTS: Fifty late-onset ATTRv-PN patients (38 men, 46 with p. A117S mutation), aged 63.7 ± 5.5 years, of polyneuropathy disability stage 1-4 were enrolled. All patients presented polyneuropathy in NCS, and 74.5% of patients had reduced IENF density in distal legs. All patients showed significant radiotracer uptake in the heart on 99m Tc-PYP SPECT imaging, and 87.8% of patients had abnormally increased left ventricular (LV) septum thickness on echocardiography. CMR showed longer myocardial native T1, larger extracellular volume, greater LV mass index, and higher LV mass to end-diastolic volume ratio in ATTRv-PN patients than healthy controls and patients with Brugada syndrome. These CMR parameters were associated with skin denervation, absent sympathetic skin responses, elevated thermal thresholds, worsened NCS profiles, and functional deficits of polyneuropathy. INTERPRETATION: Late-onset ATTRv-PN coexisted with cardiomyopathy regardless of the clinical severity of polyneuropathy. The cardiac amyloid burden revealed by CMR was correlated with pathophysiology and clinical disability of nerve degeneration.

Patterns of myelinated nerve fibers loss in transthyretin amyloid polyneuropathy and mimics.

OBJECTIVE: The present study was intended to analyze the characteristics of myelinated nerve fibers density (MFD) of transthyretin amyloid polyneuropathy (ATTR-PN) and other similar neuropathies. METHODS: A total of 41 patients with ATTR-PN, 58 patients of other common peripheral neuropathies, and 17 age-and gender-matched controls who visited the First Hospital of Peking University and performed sural nerve biopsy between June 2007 and August 2021 were included for analysis of MFD. RESULTS: Except the vasculitic neuropathy group, the total and small MFD of patients in the ATTR-PN group were significantly lower than those of other disease groups. There was an obvious negative correlation between the total MFD and the disease course in the ATTR-PN group. The disease course of early-onset and late-onset symptoms was similar, but the loss of large myelinated nerve fibers (MF) was more severe for the latter. In addition, all late-onset and most early-onset patients had severely reduced MFD after a 2 years' disease course. The MFD in ATTR-PN patients was negatively correlated with Neuropathy Impairment Score (NIS) and Norfolk Quality of life-diabetic neuropathy (Norfolk QOL-DN) score. CONCLUSION: MF is lost differently in ATTR-PN and in other common peripheral neuropathies. The late-onset and early-onset ATTR-PN patients have different patterns of loss of large and small MF.

Treatment With Diflunisal in Domino Liver Transplant Recipients With Acquired Amyloid Neuropathy.

Objectives: To analyze the efficacy and tolerability of diflunisal for the treatment of acquired amyloid neuropathy in domino liver transplant recipients. Methods: We performed a retrospective longitudinal study of prospectively collected data for all domino liver transplant recipients with acquired amyloid neuropathy who received diflunisal at our hospital. Neurological deterioration was defined as an score increase of ≥2 points from baseline on the Neurological Impairment Scale/Neurological Impairment Scale-Lower Limbs. Results: Twelve patients who had received compassionate use treatment with diflunisal were identified, of whom seven had follow-up data for ≥12 months. Five patients (71.4%) presented with neurological deterioration on the Neurological Impairment Scale after 12 months (p = 0.0382). The main adverse effects were cardiovascular and renal, leading to diflunisal being stopped in five patients and the dose being reduced in two patients. Conclusion: Our study suggests that most domino liver transplant recipients with acquired amyloid neuropathy will develop neurological deterioration by 12 months of treatment with diflunisal. This therapy was also associated with a high incidence of adverse effects and low treatment retention. The low efficacy and low tolerability of diflunisal treatment encourage the search for new therapeutic options.

Neuromuscular Complications of Systemic Amyloidosis.

Systemic amyloidosis is characterized by extracellular deposition of insoluble fibrillar proteins in multiple tissues, frequently at a distance from the site of synthesis. The 2 most common forms, light chain (AL) and transthyretin (ATTR) amyloidosis can cause peripheral neuropathy and, rarely, myopathy. Diagnosis can be challenging, and abundant suspicion is required to identify patients. As neurological manifestations of amyloidosis may precede involvement of other organs by several years, recognizing amyloid neuropathy and myopathy are crucial, especially in this new and exciting era of effective therapies for AL and ATTR neuropathy. This review will focus on the neuromuscular manifestations of AL and ATTR amyloidosis, diagnostic approaches, and recent advances in the treatment of amyloid neuropathy.

The probabilistic model of Alzheimer disease: the amyloid hypothesis revised.

The current conceptualization of Alzheimer disease (AD) is driven by the amyloid hypothesis, in which a deterministic chain of events leads from amyloid deposition and then tau deposition to neurodegeneration and progressive cognitive impairment. This model fits autosomal dominant AD but is less applicable to sporadic AD. Owing to emerging information regarding the complex biology of AD and the challenges of developing amyloid-targeting drugs, the amyloid hypothesis needs to be reconsidered. Here we propose a probabilistic model of AD in which three variants of AD (autosomal dominant AD, APOE ε4-related sporadic AD and APOE ε4-unrelated sporadic AD) feature decreasing penetrance and decreasing weight of the amyloid pathophysiological cascade, and increasing weight of stochastic factors (environmental exposures and lower-risk genes). Together, these variants account for a large share of the neuropathological and clinical variability observed in people with AD. The implementation of this model in research might lead to a better understanding of disease pathophysiology, a revision of the current clinical taxonomy and accelerated development of strategies to prevent and treat AD.

Protease-sensitive regions in amyloid light chains: what a common pattern of fragmentation across organs suggests about aggregation.

Light-chain (AL) amyloidosis is characterized by deposition of immunoglobulin light chains (LC) as fibrils in target organs. Alongside the full-length protein, abundant LC fragments are always present in AL deposits. Herein, by combining gel-based and mass spectrometry analyses, we identified and compared the fragmentation sites of amyloid LCs from multiple organs of an AL λ amyloidosis patient (AL-55). The positions pinpointed here in kidney and subcutaneous fat, alongside those previously detected in heart of the same patient, were aligned and mapped on the LC's dimeric and fibrillar states. All tissues contain fragmented LCs along with the full-length protein; the fragment pattern is coincident across organs, although microheterogeneity exists. Multiple cleavage positions were detected; some are shared, whereas some are organ-specific, likely due to a complex of proteases. Cleavage sites are concentrated in 'proteolysis-prone' regions, common to all tissues. Several proteolytic sites are not accessible on native dimers, while they are compatible with fibrils. Overall, data suggest that the heterogeneous ensemble of LC fragments originates in tissues and is consistent with digestion of preformed fibrils, or with the hypothesis that initial proteolytic cleavage of the constant domain triggers the amyloidogenic potential of LCs, followed by subsequent proteolytic degradation. This work provides a unique set of molecular data on proteolysis from ex vivo amyloid, which allows discussing hypotheses on role and timing of proteolytic events occurring along amyloid formation and accumulation in AL patients.

Pure neural leprosy or amyloid neuropathy? Systematic review and clinical case report.

OBJECTIVE: To review the literature and to report a clinical case with initial suspicion of pure neural leprosy and final diagnosis of amyloid neuropathy. METHODS: The study was conducted in two stages. In stage one, a systematic literature review was carried out, with searches performed in the PubMed, Medline, and Lilacs databases, as well as in the leprosy sectoral library of the Virtual Health Library, using the following descriptors: neuritic leprosy, pure neural leprosy, primary neural leprosy, pure neuritic leprosy, amyloid polyneuropathy, amyloid neuropathies, and amyloid polyneuropathy. The search was carried out on May 28, 2020. Clinical trials, cohort studies, cross-sectional studies, clinical cases, and case studies published in Portuguese, English or Spanish between 2010 and 2020 were included. Stage two reports a case with initial suspicion of pure neural leprosy. Laboratory tests, electroneuromyography, ultrasound, and biopsy of the sural nerve were requested. RESULTS: Twenty-three scientific texts were included. No publications were found that contained both topics together. The challenging diagnosis of pure neural leprosy and the possibility of using auxiliary resources in diagnosis were the most emphasized themes in the studies. In the clinical case, the patient's electroneuromyography showed sensitive and motor polyneuropathy of the lower limbs, which was predominantly sensory and axonal, symmetrical, of moderate intensity, and the mixed type (axonal-demyelinating). Ultrasonography of the sural nerve revealed changes in the contour of the deep fibular nerves; biopsy of the sural nerve showed an accumulation of amorphous eosinophilic material in the nerve path, and Congo red stain showed apple-green birefringence of the deposit under polarized light. The final diagnosis was amyloid neuropathy. CONCLUSIONS: The final clinical diagnosis was amyloid neuropathy. The diagnosis of pure neural leprosy in endemic areas in Brasil is still a challenge for the health system.

Quality of life assessment in amyloid transthyretin (ATTR) amyloidosis.

BACKGROUND: Amyloid transthyretin (ATTR) amyloidosis is caused by the systemic deposition of transthyretin molecules, either normal (wild-type ATTR, ATTRwt) or mutated (variant ATTR, ATTRv). ATTR amyloidosis is a disease with a severe impact on patients' quality of life (QoL). Nonetheless, limited attention has been paid to QoL so far, and no specific tools for QoL assessment in ATTR amyloidosis currently exist. QoL can be evaluated through patient-reported outcome measures (PROMs), which are completed by patients, or through scales, which are compiled by clinicians. The scales investigate QoL either directly or indirectly, i.e., by assessing the degree of functional impairment and limitations imposed by the disease. DESIGN: Search for the measures of QoL evaluated in phase 2 and phase 3 clinical trials on ATTR amyloidosis. RESULTS: Clinical trials on ATTR amyloidosis have used measures of general health status, such as the Short Form 36 Health Survey (SF-36), or tools developed in other disease settings such as the Kansas City Cardiomyopathy Questionnaire (KCCQ) or adaptations of other scales such as the modified Neuropathy Impairment Score +7 (mNIS+7). CONCLUSIONS: Scales or PROMs for ATTR amyloidosis would be useful to better characterize newly diagnosed patients and to assess disease progression and response to treatment. The ongoing ITALY (Impact of Transthyretin Amyloidosis on Life qualitY) study aims to develop and validate 2 PROMs encompassing the whole phenotypic spectrum of ATTRwt and ATTRv amyloidosis, that might be helpful for patient management and may serve as surrogate endpoints for clinical trials.

Temporal Correlation of CSF and Neuroimaging in the Amyloid-Tau-Neurodegeneration Model of Alzheimer Disease.

OBJECTIVE: To evaluate temporal correlations between CSF and neuroimaging (PET and MRI) measures of amyloid, tau, and neurodegeneration in relation to Alzheimer disease (AD) progression. METHODS: A total of 371 cognitively unimpaired and impaired participants enrolled in longitudinal studies of AD had both CSF (ß-amyloid [Aß]42, phosphorylated tau181, total tau, and neurofilament light chain) and neuroimaging (Pittsburgh compound B [PiB] PET, flortaucipir PET, and structural MRI) measures. The pairwise time interval between CSF and neuroimaging measures was binned into 2-year periods. Spearman correlations identified the time bin when CSF and neuroimaging measures most strongly correlated. CSF and neuroimaging measures were then binarized as biomarker-positive or biomarker-negative using Gaussian mixture modeling. Cohen kappa coefficient identified the time bin when CSF measures best agreed with corresponding neuroimaging measures when determining amyloid, tau, and neurodegeneration biomarker positivity. RESULTS: CSF Aß42 and PiB PET showed maximal correlation when collected within 6 years of each other (R ≈ -0.5). CSF phosphorylated tau181 and flortaucipir PET showed maximal correlation when CSF was collected 4 to 8 years prior to PET (R ≈ 0.4). CSF neurofilament light chain and cortical thickness showed low correlation, regardless of time interval (R avg ≈ -0.3). Similarly, CSF total tau and cortical thickness had low correlation, regardless of time interval (R avg < -0.2). CONCLUSIONS: CSF Aß42 and PiB PET best agree when acquired in close temporal proximity, whereas CSF phosphorylated tau precedes flortaucipir PET by 4 to 8 years. CSF and neuroimaging measures of neurodegeneration have low correspondence and are not interchangeable at any time interval.

Role of Electrostatic Interactions in Calcitonin Prefibrillar Oligomer-Induced Amyloid Neurotoxicity and Protective Effect of Neuraminidase.

Salmon calcitonin is a good model for studying amyloid behavior and neurotoxicity. Its slow aggregation rate allows the purification of low molecular weight prefibrillar oligomers, which are the most toxic species. It has been proposed that these species may cause amyloid pore formation in neuronal membranes through contact with negatively charged sialic acid residues of the ganglioside GM1. In particular, it has been proposed that an electrostatic interaction may be responsible for the initial contact between prefibrillar oligomers and GM1 contained in lipid rafts. Based on this evidence, the aim of our work was to investigate whether the neurotoxic action induced by calcitonin prefibrillar oligomers could be counteracted by treatment with neuraminidase, an enzyme that removes sialic acid residues from gangliosides. Therefore, we studied cell viability in HT22 cell lines and evaluated the effects on synaptic transmission and long-term potentiation by in vitro extracellular recordings in mouse hippocampal slices. Our results showed that treatment with neuraminidase alters the surface charges of lipid rafts, preventing interaction between the calcitonin prefibrillar oligomers and GM1, and suggesting that the enzyme, depending on the concentration used, may have a partial or total protective action in terms of cell survival and modulation of synaptic transmission.

Feasibility of assessing progression of transthyretin amyloid polyneuropathy using nerve conduction studies: Findings from the Transthyretin Amyloidosis Outcomes Survey (THAOS).

Patients with transthyretin amyloid polyneuropathy (ATTR-PN) show decreased motor and sensory nerve amplitudes and conduction. Electrophysiological changes over time may be sensitive indicators of progression. This analysis from the Transthyretin Amyloidosis Outcomes Survey (THAOS) assessed longitudinal changes in nerve conduction as signals of neurologic disease progression in patients with hereditary ATTR (ATTRv) amyloidosis. Patients with ATTRv in THAOS with recorded nerve conduction values were included (data cut-off: January 6, 2020); changes in nerve amplitude and velocity over time were assessed. Patients (n = 1389) were 45.0% male; 80.4% were the Val30Met (p.Val50Met) genotype. Mean (SD) age at enrollment was 43.6 (14.5) years; duration of symptoms was 9.3 (6.4) years. Median (10th, 90th percentile) sural nerve amplitude and velocity was 18.0 (4.9, 35.0) µV and 50.7 (41.0, 57.9) m/s; peroneal conduction was 13.0 (4.4, 27.0) µV and 51.0 (41.7, 59.7) m/s, respectively. Median (10th, 90th percentile) percentage change from baseline in sural nerve amplitude was variable, but generally decreased over time from -7.4 (-43.2, 52.4) at year 1 to -14.4 (-76.9, 46.7) at year 8. Percent change from baseline in sural nerve velocity declined similarly: -0.1 (-14.5, 15.3) at year 1 and - 6.4 (-21.3, 10.5) at year 8. The decline was more pronounced in patients with greater disability at baseline. Similar patterns were observed for the peroneal nerve. These data show an association between nerve amplitudes and velocities and disease severity, suggesting progressive deterioration in nerve conduction may be an indicator of ATTRv amyloidosis disease progression.

A circulating, disease-specific, mechanism-linked biomarker for ATTR polyneuropathy diagnosis and response to therapy prediction.

The transthyretin (TTR) amyloidoses (ATTR) are progressive, degenerative diseases resulting from dissociation of the TTR tetramer to monomers, which subsequently misfold and aggregate, forming a spectrum of aggregate structures including oligomers and amyloid fibrils. To determine whether circulating nonnative TTR (NNTTR) levels correlate with the clinical status of patients with V30M TTR familial amyloid polyneuropathy (FAP), we quantified plasma NNTTR using a newly developed sandwich enzyme-linked immunosorbent assay. The assay detected significant plasma levels of NNTTR in most presymptomatic V30M TTR carriers and in all FAP patients. NNTTR was not detected in age-matched control plasmas or in subjects with other peripheral neuropathies, suggesting NNTTR can be useful in diagnosing FAP. NNTTR levels were substantially reduced in patients receiving approved FAP disease-modifying therapies (e.g., the TTR stabilizer tafamidis, 20 mg once daily). This NNTTR decrease was seen in both the responders (average reduction 56.4 ± 4.2%; n = 49) and nonresponders (average reduction of 63.3 ± 4.8%; n = 32) at 12 mo posttreatment. Notably, high pretreatment NNTTR levels were associated with a significantly lower likelihood of clinical response to tafamidis. Our data suggest that NNTTR is a disease driver whose reduction is sufficient to ameliorate FAP so long as pretreatment NNTTR levels are below a critical clinical threshold.

Pure neural leprosy or amyloid neuropathy? Systematic review and clinical case report

SUMMARY OBJECTIVE: To review the literature and to report a clinical case with initial suspicion of pure neural leprosy and final diagnosis of amyloid neuropathy. METHODS: The study was conducted in two stages. In stage one, a systematic literature review was carried out, with searches performed in the PubMed, Medline, and Lilacs databases, as well as in the leprosy sectoral library of the Virtual Health Library, using the following descriptors: neuritic leprosy, pure neural leprosy, primary neural leprosy, pure neuritic leprosy, amyloid polyneuropathy, amyloid neuropathies, and amyloid polyneuropathy. The search was carried out on May 28, 2020. Clinical trials, cohort studies, cross-sectional studies, clinical cases, and case studies published in Portuguese, English or Spanish between 2010 and 2020 were included. Stage two reports a case with initial suspicion of pure neural leprosy. Laboratory tests, electroneuromyography, ultrasound, and biopsy of the sural nerve were requested. RESULTS: Twenty-three scientific texts were included. No publications were found that contained both topics together. The challenging diagnosis of pure neural leprosy and the possibility of using auxiliary resources in diagnosis were the most emphasized themes in the studies. In the clinical case, the patient's electroneuromyography showed sensitive and motor polyneuropathy of the lower limbs, which was predominantly sensory and axonal, symmetrical, of moderate intensity, and the mixed type (axonal-demyelinating). Ultrasonography of the sural nerve revealed changes in the contour of the deep fibular nerves; biopsy of the sural nerve showed an accumulation of amorphous eosinophilic material in the nerve path, and Congo red stain showed apple-green birefringence of the deposit under polarized light. The final diagnosis was amyloid neuropathy. CONCLUSIONS: The final clinical diagnosis was amyloid neuropathy. The diagnosis of pure neural leprosy in endemic areas in Brasil is still a challenge for the health system.