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Purpose: We describe 3 families with Charcot-Marie-Tooth neuropathy (CMT), harboring a homozygous NDUFS6 NM_004553.6:c.309+5G>A variant previously linked to fatal Leigh syndrome. We aimed to characterize clinically and molecularly the newly identified patients and understand the mechanism underlying their milder phenotype., Methods: The patients underwent extensive clinical examinations. Exome sequencing was done in 4 affected individuals. The functional effect of the c.309+5G>A variant was investigated in patient-derived EBV-transformed lymphoblasts at the complementary DNA, protein, and mitochondrial level. Alternative splicing was evaluated using complementary DNA long-read sequencing., Results: All patients presented with early-onset, slowly progressive axonal CMT, and nystagmus; some exhibited additional central nervous system symptoms. The c.309+5G>A substitution caused the expression of aberrantly spliced transcripts and negligible levels of the canonical transcript. Immunoblotting showed reduced levels of mutant isoforms. No detectable defects in mitochondrial complex stability or bioenergetics were found., Conclusion: We expand the clinical spectrum of NDUFS6-related mitochondrial disorders to include axonal CMT, emphasizing the clinical and pathophysiologic overlap between these 2 clinical entities. This work demonstrates the critical role that alternative splicing may play in modulating the severity of a genetic disorder, emphasizing the need for careful consideration when interpreting splice variants and their implications on disease prognosis., Competing Interests: Conflict of Interest The authors declare no conflicts of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background and Aims: Axonal forms of Charcot-Marie-Tooth disease (CMT) are classified as CMT2, distal hereditary motor neuropathy (dHMN) or hereditary sensory neuropathy (HSN) and can be caused by mutations in over 100 genes. We presently aimed to investigate for the first time the genetic landscape of axonal CMT in the Greek population., Methods: Sixty index patients with CMT2, dHMN or HSN were screened by a combination of Sanger sequencing (GJB1) and next-generation sequencing custom-made gene panel covering 24 commonly mutated genes in axonal CMT., Results: Overall, 20 variants classified as pathogenic or likely pathogenic were identified in heterozygous state in 20 index cases, representing 33.3% of the cohort. Of these, 14 were known pathogenic/likely pathogenic and six were designated as such according to ACMG classification, after in silico evaluation, testing for familial segregation and further literature review. The most frequently involved genes were GJB1 (11.7%), MPZ (5%) and MFN2 (5%), followed by DNM2 (3.3%) and LRSAM1 (3.3%). Single cases were identified with mutations in BSCL2, HSPB1 and GDAP1., Interpretation: A wide phenotypic variability in terms of severity and age of onset was noted. Given the limited number of genes tested, the diagnostic yield of the present panel compares favourably with studies in other European populations. Our study delineates the genetic and phenotypic variability of inherited axonal neuropathies in the Greek population and contributes to the pathogenicity characterization of further variants linked to axonal neuropathies., (© 2023 Peripheral Nerve Society.)

Purpose: Brain involvement in X-linked Charcot-Marie-Tooth disease (CMTX) has been previously reported. We studied the brain structural and functional integrity using a multimodal neuroimaging approach in patients with no current central nervous system (CNS) symptoms, in order to further delineate the disease's phenotype., Methods: Seventeen CMTX patients with no current CNS symptoms and 24 matched healthy controls underwent brain magnetic resonance imaging (MRI). Structural integrity was evaluated performing Gray matter analysis with voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS) of diffusion tensor imaging (DTI). Functional integrity was evaluated with resting-state functional MRI (rs-fMRI)., Results: Decreased gray matter density was detected in CMTX patients compared to healthy controls in bilateral hippocampus, left thalamus, left postcentral gyrus, left superior parietal lobule, left cerebellum crus I and II, and vermis VI. DTI analysis showed increased fractional anisotropy and radial diffusivity in the right anterior insula and increased axial diffusivity in right cerebellum crus I in CMTX patients. rs-fMRI revealed decreased spontaneous neural activity on left precentral gyrus in patients compared to healthy controls., Conclusion: Advanced magnetic resonance (MR) neuroimaging techniques in CMTX patients revealed structural and functional involvement of multiple motor and extra-motor brain areas. MR neuroimaging techniques have the potential to delineate the CNS phenotype of a peripheral neuropathy like CMTX., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Autosomal recessive axonal neuropathy with neuromyotonia (ARAN-NM) is a rare hereditary neuropathy within the Charcot-Marie-Tooth disease (CMT) spectrum, linked to mutations in the histidine triad nucleotide-binding protein 1 (HINT1) gene. HINT1-related neuropathy is particularly common in selected populations from Central and Eastern Europe but rare in Western European cohorts. It has not been investigated to date in the Greek population. We presently investigated the frequency of HINT1-neuropathy in a selected cohort of 42 Greek index patients with autosomal recessive or sporadic axonal hereditary neuropathy according to standard molecular genetics procedures. We identified 4 patients with biallelic mutations in HINT1, comprising 9.5% of all cases and 44.4% of cases also displaying neuromyotonia. The c.110G> C (p.Arg37Pro) HINT1 mutation was present in all cases (2 homozygous) and the c.250T> C (p.Cys84Arg) in 2 cases (compound heterozygous). HINT1-related neuropathy patients were characterized by early onset and neuromyotonia. Two patients had noteworthy clinical features, one case developing myoclonic epilepsy and the other displaying "adducted thumbs." We conclude that HINT1-related neuropathy is common in selected Greek patients with hereditary neuropathy within the CMT spectrum, in accordance with some, but not all, European populations., (© 2021 Peripheral Nerve Society.)

Objective: X-linked Charcot-Marie-Tooth disease (CMTX) is an hereditary neuropathy caused by mutations in GJB1 coding for connexin-32, found in Schwann cells, but also expressed in oligodendrocytes. Reports have identified CNS involvement in CMTX, but no systematic study of cognitive function has been published., Methods: We assessed 24 CMTX patients (13 males; 9GJB1 mutations) with a comprehensive neuropsychological battery, including tests of memory, language, and executive functions., Results: No differences in cognitive performance were observed between males and females. A case-by-case investigation revealed selective deficits in individual patients. One subgroup (29%) demonstrated executive abnormalities; and a non-overlapping subgroup (29%), prominent reading (decoding) abnormalities., Conclusions: The present data provide evidence for cognitive deficits in CMTX. Emerging neuropsychological patterns are also discussed.

Charcot-Marie-Tooth disease type 4 C (CMT4C) is an autosomal recessive form of demyelinating peripheral neuropathy caused by mutations in SH3TC2, characterized by early onset, spine deformities, and cranial nerve involvement. We screened SH3TC2 in 50 unrelated Greek patients with suspected demyelinating Charcot-Marie-Tooth disease and pedigree compatible with recessive inheritance. All patients had been previously screened for PMP22, GJB1, and MPZ mutations. We found five previously identified pathogenic mutations in SH3TC2 distributed among 13 patients in homozygosity or compound heterozygosity (p. Arg954Stop, Arg1109Stop, Gln892Stop, Ala878Asp, and Arg648Trp). Although most cases had early onset and spine deformities were almost omnipresent, a wide phenotypic spectrum was observed. Particularly notable were two siblings with Roussy-Lévy syndrome and one patient with young-onset trigeminal neuralgia. In conclusion, mutations in SH3TC2 are responsible for 26% of Greek patients with suspected CMT4, identifying CMT4C as the most common recessive demyelinating neuropathy in the Greek population, in accordance with other Mediterranean cohorts., (© 2019 Peripheral Nerve Society.)

Objective: X linked Charcot-Marie-Tooth disease (CMTX) is a hereditary neuropathy caused by mutations in GJB1 coding for connexin-32, a gap junction protein expressed in Schwann cells, but also found in oligodendrocytes. Four patients with CMTX developing central nervous system (CNS) demyelination compatible with multiple sclerosis (MS) have been individually published. We presently sought to systematically investigate the relationship between CMTX and MS., Methods: Over 20 years, 70 consecutive patients (36 men) with GJB1 mutations were identified at our Neurogenetics Unit, Athens, Greece, and assessed for clinical features suggestive of MS. Additionally, 18 patients with CMTX without CNS symptoms and 18 matched controls underwent brain MRI to investigate incidental findings. Serum from patients with CMTX and MS was tested for CNS immunoreactivity., Results: We identified three patients with CMTX who developed clinical features suggestive of inflammatory CNS demyelination fulfilling MS diagnostic criteria. The resulting 20-year MS incidence (4.3%) differed significantly from the highest background 20-year MS incidence ever reported from Greece (p=0.00039). The search for incidental brain MRI findings identified two CMTX cases (11%) with lesions suggestive of focal demyelination compared with 0 control. Moreover, 10 cases in the CMTX cohort had hyperintensity in the splenium of the corpus callosum compared with 0 control (p=0.0002). No specific CNS-reactive humoral factors were identified in patients with CMTX and MS., Conclusions: We have demonstrated a higher than expected frequency of MS in patients with CMTX and identified incidental focal demyelinating lesions on brain MRI in patients with CMTX without CNS symptoms. This provides circumstantial evidence for GJB1 mutations acting as a possible MS risk factor., Competing Interests: Competing interests: GK reports grants from Teva Pharmaceuticals and Genesis Pharma; personal fees from Novartis, Genesis Pharma, Sanofi-Genzyme and Teva Pharmaceuticals; non-financial support from Merck, Sanofi-Genzyme and Genesis Pharma; MB reports no disclosures; GV reports no disclosures; JT reports shares in a diagnostic laboratory (Tzartos Neurodiagnostics) in Athens; DK reports no disclosures; CK reports no disclosures; EK reports no disclosures; DT reports no disclosures; MA reports research grants from Biogen, Merck-Serono, Novartis, Teva, Bayer and Genzyme, as well as lecture-fees from Novartis, Teva, Biogen and Genzyme; EA reports research grants from Biogen, Merck-Serono, Novartis, and Sanofi-Aventis, as well as lecture-fees from Teva; M-EE reports consultation services and honoraria from Novartis, Biogen and Teva; CK reports research grants from Biogen, Novartis, Teva, and Merck-Serono; CP reports no disclosures; MP reports no disclosures; GK reports no disclosures., (© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Charcot-Marie-Tooth (CMT) disease, the most common hereditary neuropathy, is clinically and genetically heterogeneous. X-linked CMT (CMTX) is usually caused by mutations in the gap junction protein b 1 gene (GJB1) coding for connexin 32 (Cx32). The clinical manifestations of CMTX are characterized by significant variability, with some patients exhibiting central nervous system (CNS) involvement. We report four novel mutations in GJB1, c.191G>A (p.Cys64Tyr), c.508G>T (p.Val170Phe), c.778A>G (p.Lys260Glu) and c.300C>G (p.His100Gln) identified in four unrelated Greek families. These mutations were characterized by variable phenotypic expression, including a family with the Roussy-Lévy syndrome, and three of them were associated with mild clinical CNS manifestations., (Copyright © 2014. Published by Elsevier B.V.)

Unlabelled: The aim of the present study was to investigate the subclinical involvement of the central nervous system (CNS) in an X-linked Charcot-Marie-Toth (CMTX) family., Material and Methods: Seven subjects, all members of one family with a C.462T > G connexin 32 (Cx32) mutation were investigated by Blink reflex, Somatosensory evoked potentials (SEP) and Transcranial magnetic stimulation (TMS). There were five clinically symptomatic for CMT neuropathy (four male and one female) and two asymptomatic (female) subjects., Results: Subclinical CNS involvement was observed in all, symptomatic and asymptomatic subjects., Conclusion: This is the largest CMTX neuropathy family investigated for CNS involvement. Electrophysiological involvement of the CNS in every examined member of this family was observed, raising the question of a more systematic involvement of the CNS in CMTX disease.

Four patients from three unrelated families, with clinical and electrophysiological findings compatible with the diagnosis of hereditary motor and sensory neuropathy, are presented. The molecular analysis showed that the affected individuals were homozygous for the mutation in the X25 gene, characteristic of Friedreich's ataxia. These patients seem to represent a form of Friedreich's ataxia mimicking Charcot-Marie-Tooth disease.

OBJECTIVE Molecular analysis of hereditary motor and sensory neuropathy, Charcot-Marie-Tooth disease (CMT) in the Greek population. METHOD In total, 327 Greek index patients investigated for possible hereditary motor and sensory neuropathy at the Neurogenetics Unit of "Eginition" Hospital over a period of 15 years were included in the study, of which 243 had CMT1, 44 CMT2, and 40 hereditary neuropathy with liability to pressure palsies (HNPP). Mutational analysis was carried out using polymerase chain reaction (PCR) and Sanger sequencing, for the detection of the PMP22 duplication (CMT1A) or deletion (HNPP), and point mutations in GJB1 coding for connexin-32 (CMTX) and MPZ coding for myelin protein zero (CMT1B). In patients with CMT1, sequencing for the detection of point mutations was also carried out in PMP22 (CMT1E), EGR2 (CMT1D), LITAF (CMT1C) and NEFL (CMT1F). RESULTS In patients with CMT1 the mutation frequencies of CMT1A, CMTX, CMT1B, CMT1C, CMT1D, CMT1E and CMT1F were 25.9%, 4.9%, 0.6%, 0%, 0.6%, 1.2% and 0%, respectively. Specifically, in patients with CMT1 10 different GJB1 pathogenic mutations were detected, 5 of them novel (c.110T>C, c.208C>T, c.462T>G, c.109G>T, c.42-43insT), one novel MPZ mutation (c.89T>C), two novel PMP22 micromutations (c.296_301del CTGGAA, c.328_348dup21) and one known EGR2 mutation. In patients with CMT2, two cases were detected with the PMP22 duplication and two with a novel mutation in GJB1 (c.524A>G). The PMP22 deletion was present in 30% of the patients with HNPP. CONCLUSIONS In the Greek population, among the genetic subtypes of CMT investigated, CMT1A is the most common, followed by CMTX. CMT1E, CMT1B and CMT1D appear to be rare. The CMT1A duplication frequency is significantly lower in Greek patients with CMT than most other European populations. This may imply a special genetic characteristic of the Greek population, possibly resulting from partial genetic isolation. The frequencies of CMTX, CMT1E and CMT1D in Greek patients with CMT1 are similar to those reported in other ethnic populations. The overall frequency of MPZ mutation in Greek patients with CMT1 is one of the lowest observed to date. The PMP22 deletion frequency appears to be lower in Greek patients with HNPP than in other European populations. The absence of CMT1C and 1F in Greek patients with CMT1 is not a surprise given the rarity of these mutations in other populations. [ABSTRACT FROM AUTHOR]