Early detection of nerve involvement in presymptomatic TTR mutation carriers: exploring potential markers of disease onset.

BACKGROUND: Hereditary transthyretin (ATTRv) amyloidosis is a heterogeneous, progressive, multisystemic disease with a life-threatening course if left untreated. Given the current availability of effective therapies, close follow-up of presymptomatic TTR mutation carriers is essential to recognize disease onset at the earliest sign. In addition to routine techniques, in recent years several novel tools have been proposed, although a consensus on their use has not been reached yet. In this paper, we aimed to evaluate possible markers of neuropathic disease onset intended to discriminate clinically asymptomatic carriers from early symptomatic patients, thus allowing timely treatment initiation. METHODS: Thirty-eight presymptomatic carriers were enrolled. Clinical and electrophysiological findings at first evaluation and follow-up were collected. All carriers underwent an extensive clinical and instrumental evaluation according to the standard clinical practice. One or more non-routine investigations, whose use in this field is not yet validated (henceforth "unconventional"), were additionally assessed in a subgroup of individuals. RESULTS: Based on the exclusive use of routine investigations, it was possible to define disease onset in 4/38 carriers during the follow-up. Employing additionally one or more "unconventional" tests, abnormal findings, indicative of a possible "conversion" to symptomatic disease, were detected in further 12 cases. More than half of our study cohort showed findings suggestive of small nerve fiber (SF) involvement at either invasive or non-invasive tests. CONCLUSIONS: A close, multidisciplinary monitoring of presymptomatic TTR mutation carriers is fundamental, and diagnostic workup should include both routine and "unconventional" tests. Assessment of SF involvement is important also in non-endemic countries.

Muscle magnetic resonance imaging of a large cohort of distal hereditary motor neuropathies reveals characteristic features useful for diagnosis.

Distal motor neuropathies (dHMN) are an heterogenous group of diseases characterized by progressive muscle weakness affecting predominantly the distal muscles of the lower and upper limbs. Our aim was to study the imaging features and pattern of muscle involvement in muscle magnetic resonance imaging (MRI) in dHMN patients of suspected genetic origin (dHMN). We conducted a retrospective study collecting clinical, genetic and muscle imaging data. Muscle MRI included T1-weighted and T2 weighted Short Tau Inversion Recovery images (STIR-T2w) sequences. Muscle replacement by fat was quantified using the Mercuri score. Identification of selective patterns of involvement was performed using hierarchical clustering. Eighty-four patients with diagnosis of dHMN were studied. Fat replacement was predominant in the distal lower leg muscles (82/84 cases), although also affected thigh and pelvis muscles. Asymmetric involvement was present in 29% of patients. The superficial posterior compartment of the leg, including the soleus and gastrocnemius muscles, was the most affected area (77/84). We observed a reticular pattern of fatty replacement progressing towards what is commonly known as "muscle islands" in 79.8%. Hyperintensities in STIR-T2w were observed in 78.6% patients mainly in distal leg muscles. Besides features common to all individuals, we identified and describe a pattern of muscle fat replacement characteristic of BICD2, HSPB1 and DYNC1H1 patients. We conclude that muscle MRI of patients with suspected dHMN reveals common features helpful in diagnosis process.

Clinical Classification of Variants in the Valosin-Containing Protein Gene Associated With Multisystem Proteinopathy.

Background and Objectives: Pathogenic variants in the valosin-containing protein (VCP) gene cause a phenotypically heterogeneous disorder that includes myopathy, motor neuron disease, Paget disease of the bone, frontotemporal dementia, and parkinsonism termed multisystem proteinopathy. This hallmark pleiotropy makes the classification of novel VCP variants challenging. This retrospective study describes and assesses the effect of 19 novel or nonpreviously clinically characterized VCP variants identified in 28 patients (26 unrelated families) in the retrospective VCP International Multicenter Study. Methods: A 6-item clinical score was developed to evaluate the phenotypic level of evidence to support the pathogenicity of the novel variants. Each item is allocated a value, a score ranging from 0.5 to 5.5 points. A receiver-operating characteristic curve was used to identify a cutoff value of 3 to consider a variant as high likelihood disease associated. The scoring system results were confronted with results of in vitro ATPase activity assays and with in silico analysis. Results: All variants were missense, except for one small deletion-insertion, 18 led to amino acid changes within the N and D1 domains, and 13 increased the enzymatic activity. The clinical score coincided with the functional studies in 17 of 19 variants and with the in silico analysis in 12 of 19. For 12 variants, the 3 predictive tools agreed, and for 7 variants, the predictive tools disagreed. The pooled data supported the pathogenicity of 13 of 19 novel VCP variants identified in the study. Discussion: This study provides data to support pathogenicity of 14 of 19 novel VCP variants and provides guidance for clinicians in the evaluation of novel variants in the VCP gene.

Evaluating the contribution of the gene TARDBP in Italian patients with amyotrophic lateral sclerosis.

BACKGROUND AND OBJECTIVES: Genetic variants in the gene TARDBP, encoding TDP-43 protein, are associated with amyotrophic lateral sclerosis (ALS) in familial (fALS) and sporadic (sALS) cases. Objectives of this study were to assess the contribution of TARDBP in a large cohort of Italian ALS patients, to determine the TARDBP-associated clinical features and to look for genotype-phenotype correlation and penetrance of the mutations. METHODS: A total of 1992 Italian ALS patients (193 fALS and 1799 sALS) were enrolled in this study. Sanger sequencing of TARDBP gene was performed in patients and, when available, in patients' relatives. RESULTS: In total, 13 different rare variants were identified in 43 index cases (10 fALS and 33 sALS) with a cumulative mutational frequency of 2.2% (5.2% of fALS, 1.8% of sALS). The most prevalent variant was the p.A382T followed by the p.G294V. Cognitive impairment was detected in almost 30% of patients. While some variants, including the p.G294V and the p.G376D, were associated with restricted phenotypes, the p.A382T showed a marked clinical heterogeneity regarding age of onset, survival and association with cognitive impairment. Investigations in parents, when possible, showed that the variants were inherited from healthy carriers and never occurred de novo. CONCLUSIONS: In our cohort, TARDBP variants have a relevant frequency in Italian ALS patients and they are significantly associated with cognitive impairment. Clinical presentation is heterogeneous. Consistent genotype-phenotype correlations are limited to some mutations. A marked phenotypic variability characterizes the p.A382T variant, suggesting a multifactorial/oligogenic pathogenic mechanism.

Analysis of STMN2 CA repeats in italian ALS patients shows no association.

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease caused by a complex interaction of genetic and environmental factors. Recently, a polymorphic intronic CA repeat in STMN2 gene has been proposed as risk factor for ALS. The presence of long/long CA genotype, especially if one allele had 24 CA, was reported to be significantly associated with the disease in a cohort of sporadic ALS patients. We tested an Italian cohort of 366 ALS patients and 353 healthy controls and we found no association between CA length and ALS risk.

Pupillometric findings in ATTRv patients and carriers: results from a single-centre experience.

INTRODUCTION: Hereditary transthyretin amyloidosis (ATTRv) is a treatable multisystemic disease with great phenotypic heterogeneity. Among extra-neurological features, pupillary abnormalities have been reported, either related to amyloid deposition in the eye or to a progressive autonomic neuropathy. OBJECTIVE: To evaluate the role of automated pupillometry, a non-invasive and rapid test able to provide objective and reproducible data on pupil size and reactivity, as a marker of disease severity in late-onset ATTRv patients. PATIENTS AND METHODS: We performed automated pupillometry on a cohort of ATTRv patients and pre-symptomatic TTR mutation carriers and compared results to healthy controls. An exhaustive clinical and instrumental evaluation was performed on all enrolled subjects. RESULTS: A statistically significant difference in most pupillometry parameters was found in ATTRv patients as compared to both carriers and healthy controls. Moreover, in ATTRv patients, we found a significant correlation between many pupillometry findings and disease duration, as well as widely accepted clinical scales and investigations (NIS, Sudoscan from feet, and Norfolk QoL-DN questionnaire). CONCLUSIONS: We suggest pupillometry may play a role as a reliable and non-invasive biomarker to evaluate ATTRv disease severity and monitor its progression.

Nerve Conduction Studies of Dorsal Sural Nerve: Normative Data and Its Potential Application in ATTRv Pre-Symptomatic Subjects.

The objective of the study is to provide age-related normative values for dorsal sural nerve (DSN) and to analyse its application during follow-up of hereditary transthyretin amyloidosis (ATTRv) pre-symptomatic subjects. We consecutively recruited ATTRv pre-symptomatic carriers in which clinical examination, cardiological evaluation, and nerve conduction studies of the sural nerve and DSN were performed. To provide normative data of DSN, neurophysiologic parameters from healthy controls referred to our service were entered into linear regression analyses to check the relative influence of age and height. A correction grid was then derived. We collected 231 healthy subjects: the mean DSN sensory nerve action potential (SNAP) amplitude was 9.99 ± 5.48 µV; the mean conduction velocity was 49.01 ± 5.31 m/s. Significant correlations were found between age and height with DSN SNAP amplitude. Fifteen ATTRv pre-symptomatic carriers were examined. Sural nerve NCS were normal in 12/15 and revealed low/borderline values in three subjects. Considering our correction grid, we found an abnormal DNS amplitude in 9/15 subjects and low/borderline values in 2/15. In ATTRv, early detection of peripheral nerve damage is crucial to start a disease-modifying treatment. DSN may be easily and reliably included in the routine neurophysiological follow-up of ATTRv pre-symptomatic subjects.

Generation of an induced pluripotent stem cell line (UCSCi002-A) from a patient with a variant in TARDBP gene associated with familial amyotrophic lateral sclerosis and frontotemporal dementia.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that selectively affects motor neurons. In 20% of cases, ALS appears in comorbidity with frontotemporal dementia (FTD). We generated patient-derived-induced Pluripotent Stem Cells (iPSCs), from an ALS/FTD patient. The patient had a familial form of the disease and a missense variant in TARDBP gene. We used an established protocol based on Sendai virus to reprogram fibroblasts. We confirmed the stemness and the pluripotency of the iPSC clones, thus generating embryoid bodies. We believe that the iPSC line carrying a TARDBP mutation could be a valuable tool to investigate TDP-43 proteinopathy linked to ALS.

Progressive brachial plexus enlargement in hereditary transthyretin amyloidosis.

Axonal polyneuropathy is the main feature of hereditary transthyretin amyloidosis (ATTRv). Nerve morphological abnormalities have been reported, but longitudinal changes have never been assessed. We performed a prospective widespread nerve ultrasound evaluation and nerve cross-sectional area (CSA) was compared with baseline data in both ATTRv patients and pre-symptomatic carriers. Thirty-eight subjects were evaluated (mean follow-up 17.1 months), among them 21 had polyneuropathy while 17 were pre-symptomatic carriers. CSA significantly increased at brachial plexus in both groups (p = 0.008 and p = 0.012) pointing to progressive brachial plexus enlargement as a longitudinal biomarker of both disease progression and disease occurrence in pre-symptomatic carriers.

Thr124Met myelin protein zero mutation mimicking motor neuron disease.

Mutations in myelin protein zero (MPZ) are associated with heterogeneous manifestations. In this study, we report clinical, electrophysiological, pathological, and muscle MRI findings from two relatives with MPZ Thr124Met variants, disclosing different phenotypes. The proband was a 73-year-old female with a 12-year-story of atrophy, weakness, and fasciculations in her proximal and distal lower limbs. EMG examination showed neurogenic signs with active denervation together with reduced sensory action potentials, without sensory symptoms. The initial diagnosis was of a slowly progressive lower motor neuron disease (MND) with subclinical sensory axonal neuropathy. Two years later, the observation of her 60-year-old nephew, who had a distal sensory-motor neuropathy, prompted the analysis of inherited neuropathies-related genes and revealed a MPZ Thr124Met mutation in both cases. Our findings expand the clinical spectrum of MPZ-related neuropathy and highlight that Thr124Met mutation may cause a syndrome mimicking MND. The challenging issue to detect sensory features in the diagnostic MND work up is discussed.

Generation of an induced pluripotent stem cell line (UCSCi001-A) from a patient with early-onset amyotrophic lateral sclerosis carrying a FUS variant.

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease affecting upper and lower motor neurons. We generated patient-derived-induced Pluripotent Stem Cells (iPSCs), from an ALS patient affected by an early-onset and aggressive form of the disease, carrying a missense pathogenic variant in FUS gene. We reprogrammed somatic cells using an established Sendai virus protocol and we obtained clones of iPSC. We confirmed their stemness and further generated embryoid bodies, showing their potential of differentiating in all three germ layers. This iPSC line, carrying a pathogenic FUS variant, is a valuable tool to deeply investigate pathogenic mechanisms leading to ALS.

Patisiran in hATTR Amyloidosis: Six-Month Latency Period before Efficacy.

Hereditary amyloidosis associated with mutations in the transthyretin gene (hATTR) is a progressive devastating disease, with a fatal outcome occurring within 10years after onset. In recent years, TTR gene silencing therapy appeared as a promising therapeutic strategy, showing evidence that disease progression can be slowed and perhaps reversed. We report here 18 subjects affected by hATTR amyloidosis treated with patisiran, a small interfering RNA acting as TTR silencer, and evaluated with a PND score, the NIS and NIS-LL scale, and a Norfolk QOL-DN questionnaire at baseline and then every 6 months. A global clinical stabilizationwas observed for the majority of the patients, with mild-moderate improvements in some cases, even in advanced disease stage (PND score > 2). Analysis of NIS, NIS-LL and Norfolk QOL-DN results, and PND score variation suggest the possible presence of a 6-month latency period prior to benefit of treatment.

Novel variants and cellular studies on patients' primary fibroblasts support a role for NEK1 missense variants in ALS pathogenesis.

In the last few years, NEK1 has been identified as a new gene related to amyotrophic lateral sclerosis (ALS). Loss-of-function variants have been mostly described, although several missense variants exist, which pathogenic relevance remains to be established. We attempted to determine the contribution of NEK1 gene in an Italian cohort of 531 sporadic and familial amyotrophic lateral sclerosis (ALS) patients applying massive parallel sequencing technologies. We filtered results of NEK1 gene and identified 20 NEK1 rare variants (MAF < 0.01) in 22 patients. In particular, we found two novel frameshift variants (p.Glu929Asnfs*12 and p.Val1030Ilefs*23), 18 missense variants, including the p.Arg261His in three patients, and a novel variant in the start codon, the p.Met1?, which most likely impairs translation initiation. To clarify the role of NEK1 missense variants we investigated NEK1 expression in primary fibroblast cultures. We obtained skin biopsies from four patients with NEK1 variants and we assessed NEK1 expression by western blot and immunofluorescence. We detected a decrease in NEK1 expression in fibroblasts from patients with NEK1 variants, suggesting that missense variants in NEK1 gene may have a pathogenic role. Moreover, we observed additional variants in ALS related genes in seven patients with NEK1 variants (32%), further supporting an oligogenic ALS model.

Reassessing IVIg therapy in chronic inflammatory demyelinating polyradiculoneuropathy during COVID-19: a chance to verify the need for chronic maintenance therapy.

The outbreak of a severe acute respiratory syndrome caused by a novel coronavirus (COVID-19), has raised health concerns for patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), who are frequently on long-term immunotherapies. Treatment with IVIg does not increase the risk of contracting COVID-19, and the IVIg administration may have a protective role. However, infusions can expose patients to an increased risk of contracting SARS-CoV-2 due to repeated access to Health Facilities. In this report we analyzed the short-term follow-up of CIDP patients who modified their chronic IVIg therapy during pandemic. About half of CIDP patients regularly treated with IVIg tried to stop treatment and about 10% shifted to SCIg. Forty-two percent of the patients who stopped the treatment reported a clinical deterioration after suspension and had to restart IVIg. This study demonstrated that in selected cases it is possible to successfully stop the chronic IVIg treatment, even in patients who have been treated for several years.

A longitudinal study defined circulating microRNAs as reliable biomarkers for disease prognosis and progression in ALS human patients.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease associated with motor neuron degeneration, muscle atrophy and paralysis. To date, multiple panels of biomarkers have been described in ALS patients and murine models. Nevertheless, none of them has sufficient specificity and thus the molecular signature for ALS prognosis and progression remains to be elucidated. Here we overcome this limitation through a longitudinal study, analyzing serum levels of circulating miRNAs, stable molecules that are recently used as promising biomarkers for many types of human disorders, in ALS patients during the progression of the pathology. We performed next-generation sequencing (NGS) analysis and absolute RT quantification of serum samples of ALS patients and healthy controls. The expression levels of five selected miRNAs were quantitatively analyzed during disease progression in each patient and we demonstrated that high levels of miR-206, miR-133a and miR-151a-5p can predict a slower clinical decline of patient functionality. In particular, we found that miR-206 and miR-151a-5p serum levels were significantly up-regulated at the mild stage of ALS pathology, to decrease in the following moderate and severe stages, whereas the expression levels of miR-133a and miR-199a-5p remained low throughout the course of the disease, showing a diagnostic significance in moderate and severe stages for miR-133a and in mild and terminal ones for miR-199a-5p. Moreover, we found that miR-423-3p and 151a-5p were significantly downregulated respectively in mild and terminal stages of the disease. These data suggest that these miRNAs represent potential prognostic markers for ALS disease.

Nerve ultrasound in hereditary transthyretin amyloidosis: red flags and possible progression biomarkers.

BACKGROUND: Diagnostic delay of hereditary transthyretin amyloidosis (ATTRv, v for variant) prevents timely treatment and, therefore, concurs to the mortality of the disease. The aim of the present study was to explore with nerve ultrasound (US) possible red flags for early diagnosis in ATTRv patients with carpal tunnel syndrome (CTS) and/or polyneuropathy and in pre-symptomatic carriers. METHODS: Patients and pre-symptomatic carriers with a TTR gene mutation were enrolled from seven Italian centers. Severity of CTS was assessed with neurophysiology and clinical evaluation. Median nerve cross-section area (CSA) was measured with US in ATTRv carriers with CTS (TTR-CTS). One thousand one hundred ninety-six idiopathic CTS were used as controls. Nerve US was also performed in several nerve trunks (median, ulnar, radial, brachial plexi, tibial, peroneal, sciatic, sural) in ATTRv patients with polyneuropathy and in pre-symptomatic carriers. RESULTS: Sixty-two subjects (34 men, 28 women, mean age 59.8 years ± 12) with TTR gene mutation were recruited. With regard to CTS, while in idiopathic CTS there was a direct correlation between CTS severity and median nerve CSA (r = 0.55, p < 0.01), in the subgroup of TTR-CTS subjects (16 subjects, 5 with bilateral CTS) CSA did not significantly correlate with CTS severity (r = - 0.473). ATTRv patients with polyneuropathy showed larger CSA than pre-symptomatic carriers in several nerve sites, more pronounced at brachial plexi (p < 0.001). CONCLUSIONS: The present study identifies nerve morphological US patterns that may help in the early diagnosis (morpho-functional dissociation of median nerve in CTS) and monitoring of pre-symptomatic TTR carriers (larger nerve CSA at proximal nerve sites, especially at brachial plexi).

hATTR Pathology: Nerve Biopsy Results from Italian Referral Centers.

Pathological evidence of amyloid on nerve biopsy has been the gold standard for diagnosis in hereditary transthyretin amyloidosis polyneuropathy (hATTR-PN) for a long time. In this article, we reviewed the pathological findings of a large series of sural nerve biopsies from a cohort of hATTR-PN patients, collected by different Italian referral centers. Patients and Methods: We reviewed clinical and pathological data from hATTR-PN patients, diagnosed and followed in five Italian referral centers for peripheral neuropathies. Diagnosis was formulated after a positive genetic test for transthyretin (TTR) mutations. Sural nerve biopsy was performed according to standard protocols. Results: Sixty-nine sural nerve biopsies from hATTR-PN patients were examined. Congo red positive deposits were found in 73% of cases. Only the Phe64Leu mutation failed to show amyloid deposits in a high percentage of biopsies (54%), as already described. Unusual pathological findings, such as myelin abnormalities or inflammatory infiltrates, were detected in occasional cases. Conclusions: Even if no longer indicated to confirm hATTR-PN clinical suspicion, nerve biopsy remains, in expert hands, a rapid and inexpensive tool to detect amyloid deposition. In Italy, clinicians should be aware that a negative biopsy does not exclude hATTR-PN, particularly for Phe64Leu, one of the most frequent mutations in this country.

Small Fibre Involvement in Multifocal Motor Neuropathy Explored with Sudoscan: A Single-Centre Experience.

OBJECTIVE: Multifocal motor neuropathy (MMN) is a rare inflammatory neuropathy, clinically characterized by exclusive motor involvement. We wished to evaluate the possible presence of sensory dysfunction, including the evaluation of small fibres, after a long-term disease course. PATIENTS AND METHODS: seven MMN patients, regularly followed in our Neurology Department, underwent clinical evaluation, neurophysiological examination by nerve conduction studies (NCSs), and Sudoscan. We compared neurophysiological data with a group of patients with other disorders of the peripheral nervous system. RESULTS: NCSs showed a reduction of sensory nerve action potential amplitude in 2/7 MMN patients. Sudoscan showed borderline electrochemical skin conductance (ESC) values in 3/7 MMN patients (two of them with abnormal sensory NCSs). CONCLUSIONS: Our results confirm that sensory involvement may be found in some MMN after a long-term disease course, and it could also involve the small fibres.

High-Throughput Genetic Testing in ALS: The Challenging Path of Variant Classification Considering the ACMG Guidelines.

The development of high-throughput sequencing technologies and screening of big patient cohorts with familial and sporadic amyotrophic lateral sclerosis (ALS) led to the identification of a significant number of genetic variants, which are sometimes difficult to interpret. The American College of Medical Genetics and Genomics (ACMG) provided guidelines to help molecular geneticists and pathologists to interpret variants found in laboratory testing. We assessed the application of the ACMG criteria to ALS-related variants, combining data from literature with our experience. We analyzed a cohort of 498 ALS patients using massive parallel sequencing of ALS-associated genes and identified 280 variants with a minor allele frequency < 1%. Examining all variants using the ACMG criteria, thus considering the type of variant, inheritance, familial segregation, and possible functional studies, we classified 20 variants as "pathogenic". In conclusion, ALS's genetic complexity, such as oligogenic inheritance, presence of genes acting as risk factors, and reduced penetrance, needs to be considered when interpreting variants. The goal of this work is to provide helpful suggestions to geneticists and clinicians dealing with ALS.

Gastrointestinal Manifestations in Hereditary Transthyretin Amyloidosis: a Single-Centre Experience.

BACKGROUND AND AIMS: Hereditary transthyretin (ATTRv) amyloidosis represents a diagnostic challenge considering the great variability in clinical presentation and multiorgan involvement. In this study we report the prevalence of gastrointestinal (GI) involvement of patients with hereditary ATTRv amyloidosis from one single center of Italy, a non-endemic area. METHODS: We retrospectively analyzed a cohort of 39 patients with hereditary ATTRv amyloidosis followed at the Neurology Unit of Fondazione Policlinico Universitario A. Gemelli IRCCS in Rome, Italy. All patients had a documented mutation in the gene encoding the thansthyretin. Neurological, cardiological and gastrointestinal manifestations were systematically collected at every monitoring visit. RESULTS: 82% reported at least one GI symptom. Unintentional weight loss was the most frequently reported. Lower GI symptoms were more frequent than upper GI symptoms (66.7% vs. 35.9%, p=0.0122). The first GI symptom was always reported within 5 years since disease onset. Gastrointestinal symptoms were almost always present in patients with Val30Met mutation (93.8%, 15/16), and in more than half of the cases with Phe64Leu mutation (66.7%, 8/12). All cases with a non-Val30Met mutation disclosed almost all GI symptoms within 5 years since disease onset; conversely, patients with Val30Met mutation continued to develop further GI manifestations during the disease course. CONCLUSIONS: Prevalence of GI symptoms in our cohort was 82%, resulting in a higher prevalence than reported in the THAOS registry. Gastroenterologists, therefore, play an important role for the management of the disease, and their expertise should be valued for an effective multidisciplinary approach to this condition.