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There are few reports on axonal CMT due to dominant GDAP1 mutations. We describe two unrelated Spanish families with a dominant axonal CMT. A novel in frame GAA deletion in exon 5 of the GDAP1 gene (c.677_679del; p.R226del) was identified in both families. Disease onset varied from early childhood to adulthood. Affected family members complained of distal lower limb weakness, cramps and foot deformities with variable CMTNS score in both families. Several individuals were asymptomatic or had paraesthesia only, however neurological examination and nerve conduction studies demonstrated neuropathic signs. Transfection of HeLa cells with the p.R226del mutation led to an increased mitochondrial aggregation. We report an AD-CMT2K with large phenotypic variability due to a novel dominant GDAP1 variant. This is the second founder GDAP1 pathogenic variant reported in Spain. [ABSTRACT FROM AUTHOR]

Background and purpose: The aim of this study was to describe the frequency and distribution of SOD1 mutations in Spain, and to explore factors contributing to their phenotype and prognosis. Methods: Seventeen centres shared data on amyotrophic lateral sclerosis (ALS) patients carrying pathogenic or likely pathogenic SOD1 variants. Multivariable models were used to explore prognostic modifiers. Results: In 144 patients (from 88 families), 29 mutations (26 missense, 2 deletion/insertion and 1 frameshift) were found in all five exons of SOD1, including seven novel mutations. A total of 2.6% of ALS patients (including 17.7% familial and 1.3% sporadic) were estimated to carry SOD1 mutations. The frequency of this mutation varied considerably among regions, due to founder events. The most frequent mutation was p.Gly38Arg (n = 58), followed by p.Glu22Gly (n = 11), p.Asn140His (n = 10), and the novel p.Leu120Val (n = 10). Most mutations were characterized by a protracted course, and some of them by atypical phenotypes. Older age of onset was independently associated with faster disease progression (exp[Estimate] = 1.03 [0.01, 0.05], p = 0.001) and poorer survival (hazard ratio 1.05 [1.01, 1.08], p = 0.007), regardless of the underlying mutation. Female sex was independently associated with faster disease progression (exp[Estimate] = 2.1 [1.23, 3.65], p = 0.012) in patients carrying the p.Gly38Arg mutation, resulting in shorter survival compared with male carriers (236 vs. 301 months). Conclusions: These data may help to evaluate the efficacy of SOD1 targeted treatments, and to expand the number of patients that might benefit from these treatments. [ABSTRACT FROM AUTHOR]

Background: Guillain-Barré syndrome (GBS) is an acute inflammatory neuropathy with a heterogeneous presentation. Although some evidences support the role of autoantibodies in its pathogenesis, the target antigens remain unknown in a substantial proportion of GBS patients. The objective of this study is to screen for autoantibodies targeting peripheral nerve components in Guillain-Barré syndrome.Methods: Autoantibody screening was performed in serum samples from all GBS patients included in the International GBS Outcome study by 11 different Spanish centres. The screening included testing for anti-ganglioside antibodies, anti-nodo/paranodal antibodies, immunocytochemistry on neuroblastoma-derived human motor neurons and murine dorsal root ganglia (DRG) neurons, and immunohistochemistry on monkey peripheral nerve sections. We analysed the staining patterns of patients and controls. The prognostic value of anti-ganglioside antibodies was also analysed.Results: None of the GBS patients (n = 100) reacted against the nodo/paranodal proteins tested, and 61 (61%) were positive for, at least, one anti-ganglioside antibody. GBS sera reacted strongly against DRG neurons more frequently than controls both with IgG (6% vs 0%; p = 0.03) and IgM (11% vs 2.2%; p = 0.02) immunodetection. No differences were observed in the proportion of patients reacting against neuroblastoma-derived human motor neurons. Reactivity against monkey nerve tissue was frequently detected both in patients and controls, but specific patterns were only detected in GBS patients: IgG from 13 (13%) patients reacted strongly against Schwann cells. Finally, we confirmed that IgG anti-GM1 antibodies are associated with poorer outcomes independently of other known prognostic factors.Conclusion: Our study confirms that (1) GBS patients display a heterogeneous repertoire of autoantibodies targeting nerve cells and structures; (2) gangliosides are the most frequent antigens in GBS patients and have a prognostic value; (3) further antigen-discovery experiments may elucidate other potential antigens in GBS. [ABSTRACT FROM AUTHOR]

Background and purpose: MORC2 mutations have been described as a rare cause of axonal Charcot–Marie–Tooth disease (CMT2Z). The aim of this work was to determine the frequency and distribution of these mutations throughout Spain, to provide a comprehensive phenotypical description and, if possible, to establish a genotype–phenotype correlation. Methods: Retrospectively, data on patients diagnosed with CMT2Z in Spain were collected and clinical, electrophysiological and muscle imaging information were analysed. Results: Fifteen patients with CMT2Z were identified throughout Spain, seven of them belonging to a single kindred, whilst the rest were sporadic. The most common mutation was p.R252W, and four new mutations were identified. Eleven patients were categorized as having a scapuloperoneal phenotype, with asymmetric muscle weakness, early proximal upper limb involvement and frequent spontaneous muscular activity with distal sensory impairment and pes cavus, whilst two presented with a more classic length dependent sensory motor phenotype. This distinction was corroborated by the distribution of muscle fatty infiltration in muscle imaging. Two other patients were classified as having a neurodevelopmental phenotype consisting in congenital or early onset, delay in motor milestones, and global developmental delay in one of them. Nerve conduction studies revealed an unequivocally axonal neuropathy with frequent spontaneous activity, and serum creatine kinase levels were increased in 50% of the patients. Conclusions: MORC2 mutations are a rare cause of CMT in Spain, but in‐depth phenotyping reveals a recognizable phenotypic spectrum that will be clinically relevant for future identification of this disease. [ABSTRACT FROM AUTHOR]

GGGGCC hexanucleotide repeat expansions (HREs) in C9orf72 cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) and lead to the production of aggregating dipeptide repeat proteins (DPRs) via repeat associated non-AUG (RAN) translation. Here, we show the similar intronic GGCCTG HREs that causes spinocerebellar ataxia type 36 (SCA36) is also translated into DPRs, including poly(GP) and poly(PR). We demonstrate that poly(GP) is more abundant in SCA36 compared to c9ALS/FTD patient tissue due to canonical AUG-mediated translation from intron-retained GGCCTG repeat RNAs. However, the frequency of the antisense RAN translation product poly(PR) is comparable between c9ALS/FTD and SCA36 patient samples. Interestingly, in SCA36 patient tissue, poly(GP) exists as a soluble species, and no TDP-43 pathology is present. We show that aggregate-prone chimeric DPR (cDPR) species underlie the divergent DPR pathology between c9ALS/FTD and SCA36. These findings reveal key differences in translation, solubility, and protein aggregation of DPRs between c9ALS/FTD and SCA36. • Sense poly(GP) and antisense poly(PR) DPRs are produced in SCA36 • Unlike in c9ALS/FTD, poly(GP) is soluble and does not aggregate in SCA36 • Poly(GA:GP) chimeric DPRs underlie observed poly(GP) aggregation in c9ALS/FTD • Repeat-targeting ASOs robustly reduce poly(GP) DPRs in SCA36 McEachin et al. demonstrate that sense and antisense dipeptide repeat proteins (DPRs) present in c9ALS/FTD are also produced in the genetically similar hexanucleotide repeat expansion disorder spinocerebellar ataxia type 36 (SCA36). Poly(GP) DPRs do not aggregate in SCA36 patient tissue. Aggregate-prone, chimeric DPRs underlie divergent pathology in c9ALS/FTD and SCA36. [ABSTRACT FROM AUTHOR]