Early Onset Inherited Peripheral Neuropathies: The Experience of a Specialized Referral Center for Genetic Diagnosis Achievement

BACKGROUND

Charcot-Marie-Tooth disease (CMT) is a heterogeneous group of inherited peripheral neuropathies. Although the typical disease onset is reported in the second decade, earlier onsets are not uncommon. To date, few studies on pediatric populations have been conducted and the achievement of molecular diagnosis remains challenging.

METHODS

During the last 24 years we recruited 223 patients with early-onset hereditary peripheral neuropathies (EOHPN), negative for PMP22 duplication, 72 of them referred by a specialized pediatric hospital. Genetic testing for CMT-associated genes has been carried out with a range of different techniques.

RESULTS

Of the 223 EOHPN cases, 43% were classified as CMT1 (demyelinating), 49% as CMT2 (axonal), and 8% as CMTi (intermediate). Genetic diagnosis was reached in 51% of patients, but the diagnostic yield increased to 67% when focusing only on cases from the specialized pediatric neuromuscular centers. Excluding PMP22 rearrangements, no significant difference in diagnostic rate between demyelinating and axonal forms was identified. De novo mutations account for 38% of cases.

CONCLUSIONS

This study describes an exhaustive picture of EOHPN in an Italian referral genetic center and analyzes the molecular diagnostic rate of a heterogeneous cohort compared with one referred by a specialized pediatric center. Our data identify MPZ, MFN2, GDAP1, and SH3TC2 genes as the most frequent players in EOHPN. Our study underlines the relevance of a specific neurological pediatric expertise to address the genetic testing and highlights its importance to clarify possible unexpected results when neuropathy is only a secondary clinical sign of a more complex phenotype.

Distribution of the C9orf72 hexanucleotide repeat expansion in healthy subjects: a multicenter study promoted by the Italian IRCCS network of neuroscience and neurorehabilitation

Introduction

High repeat expansion (HRE) alleles in C9orf72 have been linked to both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD); ranges for intermediate allelic expansions have not been defined yet, and clinical interpretation of molecular data lacks a defined genotype-phenotype association. In this study, we provide results from a large multicenter epidemiological study reporting the distribution of C9orf72 repeats in healthy elderly from the Italian population.

Methods

A total of 967 samples were collected from neurologically evaluated healthy individuals over 70 years of age in the 13 institutes participating in the RIN (IRCCS Network of Neuroscience and Neurorehabilitation) based in Italy. All samples were genotyped using the AmplideXPCR/CE C9orf72 Kit (Asuragen, Inc.), using standardized protocols that have been validated through blind proficiency testing.

Results

All samples carried hexanucleotide G4C2 expansion alleles in the normal range. All samples were characterized by alleles with less than 25 repeats. In particular, 93.7% of samples showed a number of repeats ≤10, 99.9% ≤20 repeats, and 100% ≤25 repeats.

Conclusion

This study describes the distribution of hexanucleotide G4C2 expansion alleles in an Italian healthy population, providing a definition of alleles associated with the neurological healthy phenotype. Moreover, this study provides an effective model of federation between institutes, highlighting the importance of sharing genomic data and standardizing analysis techniques, promoting translational research. Data derived from the study may improve genetic counseling and future studies on ALS/FTD.

A novel de novo variant in POLR3B gene associated with a primary axonal involvement of the largest nerve fibers

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.

Case report: Episodic ataxia without ataxia?

Hereditary myopathies represent a clinically and genetically heterogeneous group of neuromuscular disorders, characterized by highly variable clinical presentations and frequently overlapping phenotypes with other neuromuscular disorders, likely influenced by genetic and environmental modifiers. Genetic testing is often challenging due to ambiguous clinical diagnosis. Here, we present the case of a family with clinical and Electromyography (EMG) features resembling a myotonia-like disorder in which Whole Exome Sequencing (WES) analysis revealed the co-segregation of two rare missense variants in UBR4 and HSPG2, genes previously associated with episodic ataxia 8 (EA8). A review of the literature highlighted a striking overlap between the clinical and the molecular features of our family and the previously described episodic ataxias (EAs), which raises concerns about the genotype-phenotype correlation, clinical variability, and the confounding overlap in these groups of disorders. This emphasizes the importance of thoroughly framing the patient's phenotype. The more clear-cut the diagnosis, the easier the identification of a genetic determinant, and the better the prognosis and the treatment of patients.

Deep sedation with dexmedetomidine administered by electrophysiologists during COVID-19 pandemic compared with propofol administered by anesthesiologists for ablation of atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background

COVID-19 pandemic, limiting the availability of anesthesiologists, has impacted heavily on the organization of invasive cardiac procedures such as transcatheter atrial fibrillation (AF) ablation.

Purpose

We compared the safety and efficacy of deep sedation with dexmedetomidine administered by electrophysiologists without anesthesiologist supervision, against the standard protocol performed with propofol.

Methods

We retrospectively included all AF ablation procedures performed in 2020: 23 patients sedated with 1% propofol (2 ml bolus followed by infusion starting at 1 mg/Kg/h), 26 patients with dexmedetomidine (infusion starting at 0.7 mcg/Kg/h). Both groups additionally received 1 mcg/Kg of midazolam as a single bolus and 0.05 mg single boluses of fentanyl prior to ablation on each pair of pulmonary veins (PV). Primary outcomes were oxygen desaturation (< 90%) or need for assisted ventilation/intubation, bradycardia (heart rate < 45 bpm) and persistent hypotension (systolic blood pressure < 90 mmHg).

Results

Baseline characteristics and hemodynamic variables did not differ between the two groups (all p > 0.05). In 8/23 (35%) patients propofol infusion velocity reduction was necessary to maintain the hemodynamic values, compared to 7/26 (27%) with dexmedetomidine.

Inter-group comparison of hemodynamic variables during the procedure showed no statistically significant difference, despite a trend in favor of dexmedetomidine (3 respiratory depressions and 3 persistent hypotension episodes with propofol vs. 0 with dexmedetomidine; p = 0.057).

Conclusion

Deep sedation with dexmedetomidine administered by electrophysiologists without anesthesiologist supervision is safe and effective for AF transcatheter ablation. A trend towards a lower incidence of hypotension and respiratory depression was noted when compared to propofol.

HeartLogic algorithm for heart failure monitoring in the era of CoViD-19 pandemic and remote monitoring/telemedicine

Background

Due to the current CoViD-19 pandemic, the number of outpatient hospital visits has significantly decreased, creating a fundamental need for telemedicine. Remote monitoring of implantable cardiac devices has emerged as a powerful and well-validated tool to follow patients with heart failure (HF) and cardiac resynchronization therapy (CRTs) devices.

Purpose

The aim of our study was to evaluate the CRT HeartLogic algorithm performance in the detection of HF episodes in a real-life population followed with remote monitoring.

Methods

Fifty-four patient (mean age 73±7 years, 72% males) with HF and reduced left ventricular ejection fraction were implanted with a HeartLogic-enabled CRT device and were enrolled in the Boston Scientific Latitude remote monitoring platform. Remote data were reviewed every month and at the time of an alert. The HeartLogic nominal value of 16 was used to trigger an alert episode. Patients were then contacted by phone and actions were taken to manage the potential HF condition detected by the alert.

Results

During a median follow-up of 12 (6–18) months, the HeartLogic alert was triggered in 9 patients (9/54, 17%). The median time between threshold crossing and a HF clinical event was 11 (2–19) days. The maximum HeartLogic index value was 43 (mean 29±8). Three events occurred after inappropriate discontinuation of HF therapy. All the events required clinical action. Four out of 9 patients required diuretic dosage increase, 1/9 electrical cardioversion for new onset atrial fibrillation, 3/9 hospitalization for i.v. therapy. One patient showed only mild HF symptoms but was found to have concomitant CoViD-19 infection.

Conclusion

The HeartLogic algorithm is useful to detect HF worsening and undertake appropriate clinical actions. Telemedicine and device remote monitoring are very helpful tools allowing early detection of HF-related clinical conditions. This is of utmost importance in the era of CoViD-19 pandemic, when scheduled access to the hospital for routine follow-up appointments might be limited.

Funding Acknowledgement

Type of funding sources: None.

A novel mutation in COL3A1 associates to vascular Ehlers-Danlos syndrome with predominant musculoskeletal involvement

Background

Vascular Ehlers–Danlos syndrome (vEDS) is a heritable connective tissue disorder caused by defects in the type III collagen protein. It is generally considered the most severe form of Ehlers–Danlos syndrome (EDS) due to an increased risk of spontaneous artery or organ rupture. vEDS has an extremely heterogeneous presentation and muscle rupture is considered a minor diagnostic criterium.

Methods

A patient with a long history of inconclusive examinations and investigations was referred to our unit. The clinical picture was mainly characterized by muscle ruptures, whereas the cardiovascular involvement was limited to mitral regurgitation. We performed a panel analysis of genes associated with inheritable heart diseases using the TruSight Cardio kit (Illumina). A skin biopsy was then performed for functional studies to analyze the different forms of collagen molecules produced in vitro by cutaneous fibroblasts.

Results

The patient presented the novel variant c.3478A>G (p.Ile1160Val) in COL3A1 (NM_000090.3), whose pathogenicity was supported by biochemical analysis of type III collagen.

Conclusion

In this report, we describe a case of vEDS with predominant and severe musculoskeletal involvement. Our findings provide insight into genetic variants and clinical expression of vEDS, broadening the clinical scenario of the syndrome.

Implantable cardiac monitor after cryptogenic stroke: atrial fibrillation detection and predictors

Objective

The main objective of our study was to analyze the incidence and predictors of atrial fibrillation (AF) in patients with cryptogenic stroke (CS) who received an implantable cardiac monitor (ICM) at our Institution.

Methods

From November 2013 to October 2017, a total of 133 patients who had suffered a CS were implanted with an ICM after a thorough screening process. The median time between the thromboembolic event and ICM implantation was 64 days [IQ range: 16–111]. All implanted patients were followed with remote monitoring until the first detected episode of AF or up to December 2018. Every remote monitoring transmission and related electrograms were analyzed by the dedicated Electrophysiology Nursing team and confirmed by experienced Electrophysiologists. AF was defined by any episode lasting greater than or equal to 2 minutes.

Results

During a median follow-up of 14.8 months [IQ range: 3.0–31.2], AF was detected in 65 out of 133 patients (48.9%). The median time from ICM implantation and AF detection was 3.5 months [IQ range: 0.9–6.7]. The prevalence of AF was 22.6%, 34.4%, 40.8% and 48.3% at 3, 6, 12 and 24 months respectively. At the multivariate analysis, high premature atrial contractions (PAC) burden and left atrium (LA) dilation were the only independent predictors of AF detection (HR 2.82, 95% CI 1.64–4.83, p&lt;0.001 for PAC; HR 1.75, 95% CI 1.03–2.97, p=0.038 for LA dimension). Patients were dived into categories based on the probability of AF detection (low, intermediate and high risk) and a new risk stratification algorithm was implemented (Figure 1).

Conclusion

After a thorough screening process, AF detection in patients with CS and ILM was quite high. Having a high PAC burden and LA dilation predicted AF episodes at the multivariate analysis. A new risk stratification algorithm was developed.

Figure 1

Funding Acknowledgement

Type of funding source: None

A novel mutation of Twinkle in Perrault syndrome: A not rare diagnosis?

Perrault syndrome is a rare disorder characterized by ovarian dysgenesis, bilateral sensorineural hearing loss and associated with mutations in six mitochondrial proteins. Additional neurological features were also described. Herein, we report on a 27-year-old woman with Perrault syndrome (PS), moderate ataxia and axonal sensory-motor peripheral neuropathy in whom we identified compound heterozygous mutations in the TWNK gene (p.Val507Ile and the novel p.Phe248Ser variant). Fewer than 30 patients with PS have been reported worldwide. Neurological involvement is more frequently associated with mutations in TWNK and indicates possible genotype-phenotype correlations. TWNK mutations should be searched in patients with sensory ataxia, early onset bilateral sensorineural hearing loss, and ovarian dysfunction in women.

Role of MAPT in Pure Motor Neuron Disease: Report of a Recurrent Mutation in Italian Patients

The aim of our study was to evaluate the role of mutations in the MAPT gene in patients with pure amyotrophic lateral sclerosis (ALS). A cohort of 120 ALS patients, both sporadic and familial, without cognitive impairment was analyzed by next-generation sequencing with a multiple-gene panel comprising 23 genes, including MAPT, known to be associated with ALS and frontotemporal dementia. The presence of the C9orf72 expansion was also investigated. Twelve patients had mutations in the SOD1, TARDBP, MATR3, and FUS genes, while 10 patients carried the C9orf72 expansion. One female patient was found to carry the D348G mutation in MAPT, previously reported in an Italian family with lower motor neuron disease. Our patient presented both upper and lower motor neuron signs, early development of dyspnea, resting and kinetic tremor, and a slow disease course (> 11 years). The present case further broadens the clinical phenotype associated with MAPT mutations and suggests that, although rarely, MAPT mutations can cause ALS and, therefore, should be analyzed in ALS patients, especially in those with early breathing difficulties and long-lasting disease.

Autosomal-dominant transthyretin (TTR)-related amyloidosis is not a frequent CMT2 neuropathy "in disguise"

Transthyretin (TTR)-related familial amyloid polyneuropathy (TTR-FAP) is a life-threatening autosomal dominant, systemic disease. First symptoms usually occur from the second to over sixth decade of life with a length-dependent axonal neuropathy with prominent involvement of the small fibers and multi-organ systemic failure.

Early diagnosis is pivotal for effective therapeutic options, but it is hampered by the heterogeneity of the clinical spectrum which can lead to misdiagnosis with other neurological condition/disorder such as axonal sensory-motor neuropathy (CMT2) as described in literature.

The aim of our study was to search for TTR mutations in a large cohort of selected undiagnosed axonal sensory-motor neuropathy patients to establish if misdiagnosis is frequent or rare in the Italian population.

No TTR pathogenic variants were found in our cohort. In conclusion, our study shows that TTR testing not should be straightforward recommended in CMT2 patients but only when “red flags” TTR’s features are present.

1993-2014: two decades of predictive testing for Huntington's disease at the Medical Genetics Unit of the University of Genoa

Background

Predictive testing for Huntington's disease has been available at the Medical Genetics Unit of the University of Genoa from 1987. In 1989, an integrated counseling protocol (geneticist, psychologist, and neurologist) was developed following International Guidelines.

Methods

This is a retrospective analysis of the clinical charts and motivation questionnaires of persons seeking predictive testing through direct DNA analysis from 1993 until 2014, with the aim to evaluate their individual characteristics, motivations, and the outcomes of the counseling protocol.

Results

A total of 299 persons (164 women, 135 men) applied for predictive testing. Most applicants’ features and motivations were similar to those previously described, but surprisingly the percentage of completed protocols was higher among men, 68.5% versus 53.5% (P = 0.011). Likewise, persons over 25 years of age were more likely to take the test than younger applicants (18–25 years): 63.4% versus 48.1% (P = 0.043). In addition, relationship status, having children, and the gender of the affected parent showed different effects on the decision about testing in males and females. No catastrophic reactions were reported during the study period.

Conclusions

We observed that factors influencing the decision‐making process might differ between males and females, and that predictive testing appears a safe procedure if framed within an integrated counseling protocol.

Two novel cases of compound heterozygous mutations in mitofusin2: Finding out the inheritance

MFN2 is the major gene involved in the axonal form of Charcot-Marie-Tooth disease. It usually has an autosomal dominant pattern of inheritance, but a few cases of homozygous or compound heterozygous mutations have been described. These patients usually present an earlier onset, more severe phenotype and their inheritance pattern can span from autosomal recessive to semidominant. Here we report two unrelated patients carrying two compound heterozygous MFN2 mutations. Both present a pure axonal neuropathy without any additional features. The first patient presents a mild clinical phenotype with onset in the 2nd decade, while the second patient shows a severe, early onset phenotype with loss of independent ambulation. Only a careful clinical examination as well as neurophysiological and genetic studies allowed us to establish the role and the transmission pattern of the identified variants. We discuss practical consequences of this finding in genetic counseling.

Complexities of Genetic Counseling for ALS: A Case of Two Siblings with Discordant Genetic Test Results

Rapid advances in the genetics of amyotrophic lateral sclerosis (ALS) have dramatically changed the approach of clinicians and researchers to the motor neuron diseases. We report two siblings in whom the genetic study provided conflicting results, hence raising a number of issues which deserve to be considered by clinicians involved in genetic testing for ALS. The first patient died within 2 years of ALS onset, while her brother still manages to walk unaided, 7 years into onset. Genetic analyses, performed on the first patient as part of a research protocol, and as clinical genetic testing on the brother, provided different results. Results for Patient 1 were negative for all investigated genes, thus suggesting that her disease may be a phenocopy, while her brother carried an autosomal dominant TARDBP mutation (p.A382T). A multidisciplinary approach may help patients and clinicians face the emerging dilemmas in such a complex field. Sharing and updating of advances, not to mention uncertainties inherent to current knowledge, with patients and families may prove to be an effective way to support them and to make them aware of the present limits of our knowledge and of the blurred border between research and clinical practice.

[Internal iliac artery: functional anastomosis value and pelvic surgery application]

The vascularization of the intra and extra pelvic organs of adults, children and neonates (male and female) is studied in 17 pelvis, in which the vascular system has been injected with colored Altufix p10 and gelatinous india ink. The pelvic region constitute a true vascular crossroad of two anastomotic networks, one arterial, originate from the visceral and parietal branches of iliac internal and external arteries, femoral and abdominal aorta by inferior mesenteric artery; the other one, which morphology is incompletely superposable in diameter. Each organ is tributary of characteristic vascular system from adventitious to mucosa with direct or recurrential manner between striated muscle fibers and mucosal layers. This duality of two systems, vascular and anastomotic provides the anatomic direction of vascular suppliance after troncular iliac artery binding and determines the vitality of the organ.

[The left renal retro-aortic vein: report of three cases]

This study investigated the congenital retro-aortic left renal vein in three subjects, observed in dissection practice. Comparative morphometric analysis is made about vein and artery and their collaterals. The importance and the contribution of this left retro-aortic renal vein are discussed with reference to his embryologic and clinical aspect implication.

[The musculo-fascial graft from the elevator muscle of the anus. Importance for plastic surgery of the bladder in the treatment of obstetric vesico-vaginal fistulas]

The levator ano-muscle and fascia are studied by females pelvis. The muscle is composed of three groups of fibres: the puborectalis muscle, the ilococcygeus and the ischiococcygeus muscles. The muscular fascial graft is dissected from the superior fibers of puborectalis muscle and placed in front of the lateral face of the bladder. In this regard, the anatomical and clinical knowledges are provided and morphometric and morphologic studies proposed this graft as the inter-vesico-vaginal plasty in treatment of vesico-vaginal fistulae.