Distal hereditary motor neuropathies.

Distal hereditary motor neuropathies (dHMN) are a group of heterogeneous hereditary disorders characterized by a slowly progressive distal pure motor neuropathy. Electrophysiology, with normal motor and sensory conduction velocities, can suggest the diagnosis of dHMN and guide the genetic study. More than thirty genes are currently associated with HMNs, but around 60 to 70% of cases of dHMN remain uncharacterized genetically. Recent cohort studies showed that HSPB1, GARS, BICB2 and DNAJB2 are among the most frequent dHMN genes and that the prevalence of the disease was calculated as 2.14 and 2.3 per 100,000. The determination of the different genes involved in dHMNs made it possible to observe a genotypic overlap with some other neurogenetic disorders and other hereditary neuropathies such as CMT2, mainly with the HSPB1, HSPB8, BICD2 and TRPV4 genes of AD-inherited transmission and recently observed with SORD gene of AR transmission which seems relatively frequent and potentially curable. Distal hereditary motor neuropathy that predominates in the upper limbs is linked mainly to three genes: GARS, BSCL2 and REEP1, whereas dHMN with vocal cord palsy is associated with SLC5A7, DCTN1 and TRPV4 genes. Among the rare AR forms of dHMN like IGHMBP2 and DNAJB2, the SIGMAR1 gene mutations as well as VRK1 variants are associated with a motor neuropathy phenotype often associated with upper motoneuron involvement. The differential diagnosis of these latter arises with juvenile forms of amyotrophic lateral sclerosis, that could be caused also by variations of these genes, as well as hereditary spastic paraplegia. A differential diagnosis of dHMN related to Brown Vialetto Van Laere syndrome due to riboflavin transporter deficiency is important to consider because of the therapeutic possibility.

Innovative Therapeutic Approaches in Congenital Myasthenic Syndromes.

Background and Objectives: To provide real-word clinical follow-up data on patients carrying variations of congenital myasthenic syndromes (CMS) and who respond to some innovative drugs. Methods: Patients recruited from the Neurology Department of the Mustapha Bacha university hospital in Algiers. Treated with innovative drugs, they were monitored and their clinical progress was evaluated on the basis of clinical arguments suggestive of CMSs, but also para clinical arguments (electromyography and genetic study). Results: Six patients carrying different mutations in different genes of CMSs were studied. They had different pathophysiologic profiles (slow or fast channel syndromes, low expressor of receptor). Their therapeutic management was based on innovative drugs, normally indicated in other, non-neurological pathologies. Their outcome was toward a clear clinical improvement. Discussion: This work relates the interest of proposing treatments (outside of Pyridostigmine) in the management of CMSs. These therapies can greatly modify the prognosis of patients suffering from this orphan disease. Classification of Evidence: This study provides Class IV evidence that for patients with congenital myasthenic syndromes, some innovative treatments are effective.

[Congenital myasthenic syndromes with kinetic abnormalities of the acetylcholine receptor]. / Les syndromes myasthéniques congénitaux avec anomalies cinétiques du récepteur à l'acétylcholine.

Congenital myasthenic syndromes (CMS) are genetically and phenotypically very heterogeneous conditions resulting in a defect in the neuromuscular transmission. Post-synaptic forms are the most frequent CMSs, and acetyl choline receptor (low expressor) deficiency is the most commonly involved pathophysiological mechanism. CMS with kinetic abnormalities of the acetylcholine receptor (AChr) are much rarer and can give rise to potentially life-threatening phenotypes. Among them, two types have been described: the slow channel syndrome (SCS) and the fast channel syndrome (FCS). Diagnosis and therapeutic management of such entities are specific to each type. In this work, we will illustrate the phenotypic aspects of CMS with kinetic abnormalities of the AChR by a narrative review of three Algerian families.

Title: Les syndromes myasthéniques congénitaux avec anomalies cinétiques du récepteur à l'acétylcholine. Abstract: Les syndromes myasthéniques congénitaux (SMC) sont des affections génétiquement et phénotypiquement très hétérogènes responsables d'un déficit de la transmission neuromusculaire. Les formes dites post-synaptiques sont les plus fréquentes des SMC, et parmi elles, le déficit en récepteur à l'acétylcholine (low expressor) est le mécanisme physiopathologique le plus souvent en cause. Les SMC avec anomalies cinétiques du récepteur à l'acétylcholine sont beaucoup plus rares et à l'origine de tableaux cliniques à l'issue parfois dramatique. On en dénombre deux types : le syndrome du canal lent et le syndrome du canal rapide. Leur diagnostic et leur prise en charge thérapeutique sont spécifiques à chaque type. Dans ce travail, nous détaillerons leurs aspects phénotypiques respectifs en les illustrant par les observations de trois familles algériennes.

Loss of phospholipase PLAAT3 causes a mixed lipodystrophic and neurological syndrome due to impaired PPARγ signaling.

Phospholipase A/acyltransferase 3 (PLAAT3) is a phospholipid-modifying enzyme predominantly expressed in neural and white adipose tissue (WAT). It is a potential drug target for metabolic syndrome, as Plaat3 deficiency in mice protects against diet-induced obesity. We identified seven patients from four unrelated consanguineous families, with homozygous loss-of-function variants in PLAAT3, who presented with a lipodystrophy syndrome with loss of fat varying from partial to generalized and associated with metabolic complications, as well as variable neurological features including demyelinating neuropathy and intellectual disability. Multi-omics analysis of mouse Plaat3-/- and patient-derived WAT showed enrichment of arachidonic acid-containing membrane phospholipids and a strong decrease in the signaling of peroxisome proliferator-activated receptor gamma (PPARγ), the master regulator of adipocyte differentiation. Accordingly, CRISPR-Cas9-mediated PLAAT3 inactivation in human adipose stem cells induced insulin resistance, altered adipocyte differentiation with decreased lipid droplet formation and reduced the expression of adipogenic and mature adipocyte markers, including PPARγ. These findings establish PLAAT3 deficiency as a hereditary lipodystrophy syndrome with neurological manifestations, caused by a PPARγ-dependent defect in WAT differentiation and function.

The methylenetetrahydrofolate reductase C677T and A1298C genetic polymorphisms and plasma homocysteine in Alzheimer's disease in an Algerian population.

BACKGROUND: The etiology of Alzheimer's disease (AD) is multifactorial. The most important challenge of research is the identification of potential biomarkers associated with AD pathogenesis that may significantly contribute to early diagnosis of the disease. We aim to explore an eventual association of the C677T and A1298C genetic polymorphisms in the MTHFR gene with AD risk in an Algerian population. METHODS: This case-control study involved comparing a group of 106 patients that had developed AD to another group of 104 non-demented individuals. The MTHFR genotypes were determined using PCR-RFLP method. Additionally, the homocysteine level was evaluated. RESULTS: Genotypes analysis did not show an association for both MTHFR677CT and 677TT variants with AD risk (OR = 1.12; p = 0.66; OR = 1.76; p = 0.09) respectively. As expected, the 677CC wild type genotype showed a protective role against AD (OR = 0.52; p = 0.03). For 1298AC MTHFR variant, the distribution of different genotypes did not show a statistical significant difference between the two cohorts. However the silmutaneous carrier, CT/AC presented association with AD (OR = 5.96; p = 0.05). On the other hand, carrier-state of MTHFR T allele showed a relationship with AD (OR = 1.98; p = 0.02). Additionally, hyperhomocysteinemia seems to be a risk factor for AD (OR = 1.08; p = 0.02). CONCLUSION: Our exploration reveals that the silmutaneous carrier, CT/AC, carrier-state of MTHFR T allele, and hyperhomocysteinemia seem to be risk factors for AD.

Moderate phenotype of a congenital myasthenic syndrome type 19 caused by mutation of the COL13A1 gene: a case report.

BACKGROUND: Congenital myasthenic syndromes caused by mutations in the COL13A1 gene are very rare and have a phenotype described as severe. We present the first case of congenital myasthenic syndrome described in Algeria and the Maghreb with a new mutation of this gene. CASE PRESENTATION: We present an 8-year-old Algerian female patient, who presented with a moderate phenotype with bilateral ptosis that fluctuates during the day and has occurred since birth. During the investigation, and despite the very probable congenital origin, we ruled out other diagnoses that could induce pathology of the neuromuscular junction. The genetic study confirmed our diagnosis suspicion by highlighting a new mutation in the COL13A1 gene. CONCLUSION: We report a case with a mutation of the Col13A1 gene, reported in the Maghreb (North Africa), and whose phenotype is moderate compared with the majority of cases found in the literature.

Clinical management and disease-modifying treatment for amyotrophic lateral sclerosis in African hospital centers: the TROPALS study.

Objective: To assess the availability of health workers and medications for clinical management of amyotrophic lateral sclerosis (ALS) in African hospital centers. Availability and affordability analyses of disease-modifying treatments were performed. Methods: A multicenter observational study involving African hospitals was conducted. A standard questionnaire was developed based on the European Federation of the Neurological Societies (EFNS) guidelines. We collected data on multidisciplinary care and availability of medicines. The availability and affordability were evaluated according to the WHO guidelines. Results: Nine hospital centers from eight African countries participated. We observed a low degree of implementation of multidisciplinary care in ALS management. Riluzole was only available in centers from South Africa, Senegal, Tunisia, and Togo. This treatment was unaffordable and the adjusted price was highly variable among countries. The cost of riluzole was partly or fully covered by patients, which implies a substantial economic burden. Conclusion: Our findings strengthen the need to promote multidisciplinary care in the clinical management of ALS in Africa. Disease-modifying medication should be both available and affordable. Local and international collaboration is needed to improve ALS health care access in Africa.

[The high phenotypic variability of RYR1 gene mutations]. / La grande variabilité phénotypique des mutations du gène RYR1.

The RYR1 gene encodes the ryanodine-receptor 1, a key protein in the excitation-contraction coupling that takes place in muscle fibers. This receptor is the main channel responsible for calcium release from the endoplasmic reticulum [1]. A number of clinical phenotypes are linked to various mutations in this large gene as shown in a compilation established by ORPHANET (see table). In this work we describe two distinct, somewhat misleading, phenotypes in relation to pathogenic variants in this gene.

Title: La grande variabilité phénotypique des mutations du gène RYR1. Abstract: Le gène RYR1 (Ryanodine-Receptor-1) code pour une protéine-clé dans le processus de couplage excitation-contraction de la fibre musculaire. Ce récepteur est le principal canal de libération du calcium à partir du réticulum endoplasmique [1]. Un certain nombre de phénotypes cliniques sont imputables aux mutations de ce gène de grande taille comme rappelé dans la liste établie par ORPHANET (voir Encadré). Nous décrivons, dans ce travail, deux phénotypes distincts, et trompeurs à certains égards, en rapport avec des mutations de ce gène.

NTRK1 gene-related congenital insensitivity to pain with anhidrosis: a nationwide multicenter retrospective study.

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare autosomal recessive disease resulting from mutations in the NTRK1 gene encoding the neurotrophic tyrosine kinase-1 receptor. In this multicenter observational retrospective study, we investigated CIPA patients identified from French laboratories sequencing the NTRK1 gene, and seven patients were identified. Patients originated from France (2), Suriname (2), Mali (1), Kazakhstan (1), and Algeria (1). Mean age of patients was 9.8 years (4-20), four patients were female (57%), infant developmental milestones were delayed in four cases (57%), and four patients had a family history of consanguinity (57%). Mean age at diagnosis was 4.8 months (3-6), and all patients presented with pain insensitivity, anhidrosis, intellectual disability, self-mutilation, febrile episodes, impaired temperature perception, and autonomous nervous system impairment. Patients also showed an assortment of associated findings, including hyperactivity (86%), emotional lability (86%), joint deformities (71%), bone fractures (57%), abnormal sense of touch, vibration and position (50%), skin, hair and nails abnormalities (28%), and hypothermia episodes (28%). Two patients died at age 9 and 12 years from infection. In three cases, nerve conduction studies showed absent lower limbs sensory nerve action potentials. In one case, sensory nerve biopsy showed complete absence of unmyelinated fibers. Nine NTRK1 pathogenic variants were found, including three newly described mutations. This nationwide study confirms that NTRK1 gene-related CIPA is an extremely rare disorder and expands the genotypic spectrum of NTRK1 mutations.

Increasing involvement of CAPN1 variants in spastic ataxias and phenotype-genotype correlations.

Spastic ataxias are rare neurogenetic disorders involving spinocerebellar and pyramidal tracts. Many genes are involved. Among them, CAPN1, when mutated, is responsible for a complex inherited form of spastic paraplegia (SPG76). We report the largest published series of 21 novel patients with nine new CAPN1 disease-causing variants and their clinical characteristics from two European university hospitals (Paris and Stockholm). After a formal clinical examination, causative variants were identified by next-generation sequencing and confirmed by Sanger sequencing. CAPN1 variants are a rare cause (~ 1.4%) of young-adult-onset spastic ataxia; however, together with all published cases, they allowed us to better describe the clinical and genetic spectra of this form. Truncating variants are the most frequent, and missense variants lead to earlier age at onset in favor of an additional deleterious effect. Cerebellar ataxia with cerebellar atrophy, dysarthria and lower limb weakness are often associated with spasticity. We also suggest that cognitive impairment and depression should be assessed specifically in the follow-up of SPG76 cases.

Characterization of Recessive Parkinson Disease in a Large Multicenter Study.

Studies of the phenotype and population distribution of rare genetic forms of parkinsonism are required, now that gene-targeting approaches for Parkinson disease have reached the clinical trial stage. We evaluated the frequencies of PRKN, PINK1, and DJ-1 mutations in a cohort of 1,587 cases. Mutations were found in 14.1% of patients; 27.6% were familial and 8% were isolated. PRKN was the gene most frequently mutated in Caucasians, whereas PINK1 mutations predominated in Arab-Berber individuals. Patients with PRKN mutations had an earlier age at onset, and less asymmetry, levodopa-induced motor complications, dysautonomia, and dementia than those without mutations. ANN NEUROL 2020;88:843-850.

Nonsteroidal Anti-inflammatory Use and LRRK2 Parkinson's Disease Penetrance.

BACKGROUND: The penetrance of leucine rich repeat kinase 2 (LRRK2) mutations is incomplete and may be influenced by environmental and/or other genetic factors. Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to reduce inflammation and may lower Parkinson's disease (PD) risk, but their role in LRRK2-associated PD is unknown. OBJECTIVES: The objective of this study is to evaluate the association of regular NSAID use and LRRK2-associated PD. METHODS: Symptomatic ("LRRK2-PD") and asymptomatic ("LRRK2-non-PD") participants with LRRK2 G2019S, R1441X, or I2020T variants (definitely pathogenic variant carriers) or G2385R or R1628P variants (risk variant carriers) from 2 international cohorts provided information on regular ibuprofen and/or aspirin use (≥2 pills/week for ≥6 months) prior to the index date (diagnosis date for PD, interview date for non-PD). Multivariate logistic regression was used to evaluate the relationship between regular NSAID use and PD for any NSAID, separately for ibuprofen and aspirin in all carriers and separately in pathogenic and risk variant groups. RESULTS: A total of 259 LRRK2-PD and 318 LRRK2-non-PD participants were enrolled. Regular NSAID use was associated with reduced odds of PD in the overall cohort (odds ratio [OR], 0.34; 95% confidence interval [CI], 0.21-0.57) and in both pathogenic and risk variant carriers (ORPathogenic , 0.38; 95% CI, 0.21-0.67 and ORRiskVariant , 0.19; 95% CI, 0.04-0.99). Similar associations were observed for ibuprofen and aspirin separately (ORIbuprofen , 0.19; 95% CI, 0.07-0.50 and ORAspirin , 0.51; 95% CI, 0.28-0.91). CONCLUSIONS: Regular NSAID use may be associated with reduced penetrance in LRRK2-associated PD. The LRRK2 protein is involved in inflammatory pathways and appears to be modulated by regular anti-inflammatory use. Longitudinal observational and interventional studies of NSAID exposure and LRRK2-PD are needed to confirm this association. © 2020 International Parkinson and Movement Disorder Society.

A multicenter retrospective study of charcot-marie-tooth disease type 4B (CMT4B) associated with mutations in myotubularin-related proteins (MTMRs).

OBJECTIVE: Charcot-Marie-Tooth (CMT) disease 4B1 and 4B2 (CMT4B1/B2) are characterized by recessive inheritance, early onset, severe course, slowed nerve conduction, and myelin outfoldings. CMT4B3 shows a more heterogeneous phenotype. All are associated with myotubularin-related protein (MTMR) mutations. We conducted a multicenter, retrospective study to better characterize CMT4B. METHODS: We collected clinical and genetic data from CMT4B subjects in 18 centers using a predefined minimal data set including Medical Research Council (MRC) scores of nine muscle pairs and CMT Neuropathy Score. RESULTS: There were 50 patients, 21 of whom never reported before, carrying 44 mutations, of which 21 were novel and six representing novel disease associations of known rare variants. CMT4B1 patients had significantly more-severe disease than CMT4B2, with earlier onset, more-frequent motor milestones delay, wheelchair use, and respiratory involvement as well as worse MRC scores and motor CMT Examination Score components despite younger age at examination. Vocal cord involvement was common in both subtypes, whereas glaucoma occurred in CMT4B2 only. Nerve conduction velocities were similarly slowed in both subtypes. Regression analyses showed that disease severity is significantly associated with age in CMT4B1. Slopes are steeper for CMT4B1, indicating faster disease progression. Almost none of the mutations in the MTMR2 and MTMR13 genes, responsible for CMT4B1 and B2, respectively, influence the correlation between disease severity and age, in agreement with the hypothesis of a complete loss of function of MTMR2/13 proteins for such mutations. INTERPRETATION: This is the largest CMT4B series ever reported, demonstrating that CMT4B1 is significantly more severe than CMT4B2, and allowing an estimate of prognosis. ANN NEUROL 2019.

Clinical features and prognosis of amyotrophic lateral sclerosis in Africa: the TROPALS study.

OBJECTIVE: We describe and compare the sociodemographic and clinical features, treatments, and prognoses and survival times of patients with amyotrophic lateral sclerosis (ALS) in Africa. METHODOLOGY: We conducted a multicentre, hospital-based cohort study in Africa. Patients with ALS diagnosed in the neurology departments of participating hospitals from 2005 to 2017 were included. Subgroup analysis was performed by subcontinent. Survival analyses were conducted using the Cox proportional hazards model. RESULTS: Nine centres from eight African countries participated. A total of 185 patients with ALS were included: 114 from Northern Africa, 41 from Western Africa and 30 from Southern Africa. A male predominance (male to female ratio 2.9) was evident. The median age at onset was 53.0 years (IQR 44.5-64.0 years). The onset was bulbar in 22.7%. Only 47 patients (26.3%) received riluzole, mainly in Northern and Western Africa. The median survival from the time of diagnosis was 14.0 months (95% CI 10.7 to 17.2 months). The median survival was longer in Northern Africa (19.0 months, 95% CI 10.8 to 27.2 months) than in Western (4.0 months, 95% CI 0.8 to 7.1 months) and Southern (11.0 months, 95% CI 5.6 to 16.4 months) Africa (Breslow test, p<0.0001). Both subcontinental location and riluzole treatment independently affected survival. CONCLUSION: More African patients with ALS were male and younger and exhibited a lower proportion of bulbar onset compared with patients with ALS from Western nations. Survival was consistent with that in Western registers but far shorter than what would be expected for young patients with ALS. The research improves our understanding of the disease in Africa.

Updating the classification of inherited neuropathies: Results of an international survey.

OBJECTIVE: The continual discovery of disease-causing gene mutations has led to difficulties in the complex classification of Charcot-Marie-Tooth diseases (CMT) that needs to be revised. METHODS: We recently published a proposal to update the classification of inherited neuropathies. The reactions from colleagues prompted us to diffuse the proposal and ask people if they would be ready for such a change. We therefore performed an internet survey (from October 1, 2016, to December 1, 2016) that included more than 300 CMT worldwide specialists (practitioners and scientists) from various countries. A questionnaire (with proposals to update and simplify the way in which CMT is classified) was sent by e-mail to all participants in the last International Charcot-Marie-Tooth and Related Neuropathy Consortium meeting held in Venice, September 8-10, 2016 (as identified through an e-mail list). RESULTS: Of the 107 CMT specialists who answered the survey, 65% considered that changes are needed and that our proposals constituted an improvement over the historical classification of CMT. CONCLUSIONS: Based on recent proposals in the medical literature, these results highlight that most specialists think that changes are needed to the classification of CMT.

Nerve Biopsy Is Still Useful in Some Inherited Neuropathies.

In hereditary neuropathies, next-generation sequencing techniques are producing a vast number of candidate gene mutations that need to be verified or excluded by careful genotype-phenotype correlation analysis. In most cases, clinical acumen is still important but needs to be combined with data from nerve conduction studies and, in some cases, from nerve biopsy examinations. Indeed, characteristic clinical, electrophysiological, and sometimes pathological features may be suggestive of a particular subtype of Charcot-Marie-Tooth (CMT) disease. Microscopical (mainly ultrastructural) human nerve biopsy patterns may be related to CMT diseases and gene defects. Even today, it is important to recognize these characteristic lesions in the context of a chronic idiopathic neuropathy as they may help search for or reveal a sporadic form of CMT. In practice, these different types of lesions are often linked to the known function of the mutated genes. Only a few patients diagnosed or suspected as having a CMT disease need a nerve biopsy that can help find or confirm the causative gene mutation. The indication for this procedure should be based on a case-by-case discussion.

Clinical, Biomarker, and Molecular Delineations and Genotype-Phenotype Correlations of Ataxia With Oculomotor Apraxia Type 1.

Importance: Ataxia with oculomotor apraxia type 1 (AOA1) is an autosomal recessive cerebellar ataxia due to mutations in the aprataxin gene (APTX) that is characterized by early-onset cerebellar ataxia, oculomotor apraxia, axonal motor neuropathy, and eventual decrease of albumin serum levels. Objectives: To improve the clinical, biomarker, and molecular delineation of AOA1 and provide genotype-phenotype correlations. Design, Setting, and Participants: This retrospective analysis included the clinical, biological (especially regarding biomarkers of the disease), electrophysiologic, imaging, and molecular data of all patients consecutively diagnosed with AOA1 in a single genetics laboratory from January 1, 2002, through December 31, 2014. Data were analyzed from January 1, 2015, through January 31, 2016. Main Outcomes and Measures: The clinical, biological, and molecular spectrum of AOA1 and genotype-phenotype correlations. Results: The diagnosis of AOA1 was confirmed in 80 patients (46 men [58%] and 34 women [42%]; mean [SD] age at onset, 7.7 [7.4] years) from 51 families, including 57 new (with 8 new mutations) and 23 previously described patients. Elevated levels of α-fetoprotein (AFP) were found in 33 patients (41%); hypoalbuminemia, in 50 (63%). Median AFP level was higher in patients with AOA1 (6.0 ng/mL; range, 1.1-17.0 ng/mL) than in patients without ataxia (3.4 ng/mL; range, 0.8-17.2 ng/mL; P < .01). Decreased albumin levels (ρ = -0.532) and elevated AFP levels (ρ = 0.637) were correlated with disease duration. The p.Trp279* mutation, initially reported as restricted to the Portuguese founder haplotype, was discovered in 53 patients with AOA1 (66%) with broad white racial origins. Oculomotor apraxia was found in 49 patients (61%); polyneuropathy, in 74 (93%); and cerebellar atrophy, in 78 (98%). Oculomotor apraxia correlated with the severity of ataxia and mutation type, being more frequent with deletion or truncating mutations (83%) than with presence of at least 1 missense variant (17%; P < .01). Mean (SD) age at onset was higher for patients with at least 1 missense mutation (17.7 [11.4] vs 5.2 [2.6] years; P < .001). Conclusions and Relevance: The AFP level, slightly elevated in a substantial fraction of patients, may constitute a new biomarker for AOA1. Oculomotor apraxia may be an optional finding in AOA1 and correlates with more severe disease. The p.Trp279* mutation is the most frequent APTX mutation in the white population. APTX missense mutations may be associated with a milder phenotype.