Trigeminal neuralgia, demyelinating polyneuropathy, and central nervous system involvement in a patient with an SH3TC2 mutation.

BACKGROUND: Charcot-Marie-Tooth type 4C (CMT4C) is a slowly progressive, autosomal recessive, sensorimotor polyneuropathy characterized by demyelination and distinct clinical features, including cranial nerve involvement. CMT4C is associated with pathogenic mutations in the SH3TC2 gene. METHODS: A patient presenting with gait instability due to demyelinating polyneuropathy and refractory trigeminal neuralgia underwent comprehensive evaluation. Nerve conduction studies, magnetic resonance imaging (MRI) of the brain, cervical spine, and thoracic spine, lumbar puncture, and genetic test through next generation sequencing were performed. RESULTS: The genetic test found an Arg1109Stop mutation in the SH3TC2 gene, associated with demyelinating polyneuropathy and cranial neuropathy. Interestingly, brain MRI showed multiple, nonenhancing white matter hyperintensities. This is the first case of CMT4C associated with white matter lesions. CONCLUSION: Any patient with slowly progressive peripheral nervous system symptoms and disproportionally abnormal nerve conduction study findings should be tested for an inherited polyneuropathy and brain imaging for screening of possible central nervous system involvement should be performed. Further investigation is needed to elucidate the pathogenetic basis of CMT4C and a possible association with white matter lesions.

Genetic Landscape of SH3TC2 variants in Russian patients with Charcot-Marie-Tooth disease.

Introduction: Charcot-Marie-Tooth disease type 4C (CMT4C) OMIM#601596 stands out as one of the most prevalent forms of recessive motor sensory neuropathy worldwide. This disorder results from biallelic pathogenic variants in the SH3TC2 gene. Methods: Within a cohort comprising 700 unrelated Russian patients diagnosed with Charcot-Marie-Tooth disease, we conducted a gene panel analysis encompassing 21 genes associated with hereditary neuropathies. Among the cohort, 394 individuals exhibited demyelinating motor and sensory neuropathy. Results and discussion: Notably, 10 cases of CMT4C were identified within this cohort. The prevalence of CMT4C among Russian demyelinating CMT patients lacking the PMP22 duplication is estimated at 2.5%, significantly differing from observations in European populations. In total, 4 novel and 9 previously reported variants in the SH3TC2 gene were identified. No accumulation of a major variant was detected. Three previously reported variants, c.2860C>T p. (Arg954*), p. (Arg658Cys) and c.279G>A p. (Lys93Lys), recurrently detected in unrelated families. Nucleotide alteration p. (Arg954*) is present in most of our patients (30%).

Characterisation of Patients with SH3TC2 Associated Neuropathy in an Indian Cohort.

Background: SH3TC2 variations lead to demyelinating recessive Charcot-Marie-Tooth (CMT) disease, which is commonly associated with early-onset scoliosis and cranial neuropathy. Data from Indian ethnicity is limited. Objective: We aim to report the characteristics of patients with SH3TC2-associated neuropathy from an Indian cohort. Patients and Methods: Data of five unrelated subjects with SH3TC2 variations were analyzed. Results: Clinical features included female predominance (n = 4), early-onset neuropathy (n = 2), pes cavus and hammer toes (n = 4), kyphoscoliosis (n = 1), impaired vision and hearing (n = 1), facial muscle weakness (n = 1), impaired kinaesthetic sense (n = 3), tremor (n = 2), and ataxia (n = 1). Four patients had the "CMT" phenotype, while one patient had Roussy-Levy syndrome. All had demyelinating electrophysiology with conduction velocities being "very slow" in one, "slow" in one, "mildly slow" in two, and "intermediate" in one patient. Brain stem auditory evoked potentials were universally abnormal though only one patient had symptomatic deafness. Seven variants were identified in SH3TC2 [homozygous = 3 (c.1412del, c.69del, c.3152G>A), heterozygous = 4 (c.1105C>T, c.3511C>T, c.2028G>C, c.254A>T)]. Except for c.3511C>T variant, the rest were novel. Three patients had additional variations in genes having pathobiological relevance in other CMTs or amyotrophic lateral sclerosis. Conclusion: We provide data on a cohort of patients of Indian origin with SH3TC2 variations and highlight differences from other cohorts. Though the majority were not symptomatic for hearing impairment, evoked potentials disclosed abnormalities in all. Further studies are required to establish the functional consequences of novel variants and their interacting molecular partners identified in the present study to strengthen their association with the phenotype.

Neuropathy due to bi-allelic SH3TC2 variants: genotype-phenotype correlation and natural history.

Recessive SH3TC2 variants cause Charcot-Marie-Tooth disease type 4C (CMT4C). CMT4C is typically a sensorimotor demyelinating polyneuropathy, marked by early onset spinal deformities, but its clinical characteristics and severity are quite variable. Clear relationships between pathogenic variants and the spectrum of disease manifestations are to date lacking. Gene replacement therapy has been shown to ameliorate the phenotype in a mouse model of CMT4C, emphasizing the need for natural history studies to inform clinical trial readiness. Data, including both genetic information and clinical characteristics, were compiled from the longitudinal, prospective dataset of the Inherited Neuropathy Consortium, a member of the Rare Diseases Clinical Research Network (INC-RDCRN). The Charcot Marie Tooth Neuropathy Score (CMTNS), Examination Score (CMTES) and the Rasch-weighted CMTES (CMTES-R) were used to describe symptoms, neurological examinations and neurophysiological characteristics. Standardized response means were calculated at yearly intervals and a mixed model for repeated measures was used to estimate the change in CMTES and CMTES-R over time. Fifty-six individuals (59% female), median age 27 years (range 2-67 years) with homozygous or compound heterozygous variants in SH3TC2 were identified, including 34 unique variants, 14 of which have not previously been published. Twenty-eight participants had longitudinal data available. While there was no significant difference in the CMTES in those with protein truncating versus non-protein truncating variants, there were significant differences in the mean ulnar nerve compound muscle action potential amplitude, the mean radial sensory nerve action potential amplitude, and in the prevalence of scoliosis, suggesting the possibility of a milder phenotype in individuals with one or two non-protein-truncating variants. Overall, the mean value of the CMTES was 13, reflecting moderate clinical severity. There was a high rate of scoliosis (81%), scoliosis surgery (36%), and walking difficulty (94%) among study participants. The CMTES and CMTES-R appeared moderately responsive to change over extended follow-up, demonstrating a standardized response mean of 0.81 standard deviation units or 0.71 standard deviation units, respectively, over 3 years. Our analysis represents the largest cross-sectional and only longitudinal study to date, of the clinical phenotype of both adults and children with CMT4C. With the promise of upcoming genetic treatments, these data will further define the natural history of the disease and inform study design in preparation for clinical trials.

Characteristics of Clinical and Electrophysiological Pattern in a Large Cohort of Chinese Patients With Charcot-Marie-Tooth 4C.

The "Src homology 3 (SH3) domain and tetratricopeptide repeats 2" (SH3TC2) gene is mutated in individuals with Charcot-Marie-Tooth disease (CMT) and considered relevant to a demyelinating or intermediate subtype of CMT disease, CMT4C. In this study, we screened a cohort of 465 unrelated Chinese CMT patients alongside 650 controls. We used Sanger, next-generation, or whole-exome sequencing to analyze SH3TC2 and other CMT-related genes and identified 12 SH3TC2 variants (eight novel) in seven families. Of the eight novel variants, seven were likely pathogenic (c.280-2 A > G, c.732-1 G > A, c.1177+6 T > C, c.3328-1 G > A, G299S, R548W, L1048P), and 1 had uncertain significance (S221P). The CMT4C frequency was calculated to be 4.24% in demyelinating or intermediate CMT patients without PMP22 duplication. Additionally, we detected variant R954* in the Chinese cohort in our study, indicating that this variant may be present among Asians, albeit with a relatively low frequency. The onset age varied among the eight patients, three of whom presented scoliosis. We summarized phenotypes in the Chinese CMT cohort and concluded that the absence of scoliosis, cranial nerve involvement, or late-onset symptoms does not necessarily preclude SH3TC2 involvement in a given case.

Dropped head syndrome as a manifestation of Charcot-Marie-Tooth disease type 4C.

Charcot Marie Tooth disease type 4C (CMT4C) is considered the most frequent autosomal recessive form of CMT worldwide, being described as an early-onset disorder with marked clinical heterogeneity. We report a CMT4C case associated with dropped head syndrome and predominant involvement of proximal muscles. An 11-year-old boy born to consanguineous parents presented with predominantly proximal muscle weakness with facial involvement, associated with dropped head and severe scoliosis. Symptoms started at the age of 3 years-old with frequent falls. Nerve conduction studies showed a sensorimotor demyelinating polyneuropathy. A comprehensive multigene next-generation sequencing panel for CMT revealed the homozygous pathogenic missense variant c.1969G > A (p.E657K) in SH3TC2 gene, confirming CMT4C diagnosis. The present report broadens the phenotype associated with CMT4C and raises the importance of considering early-onset inherited polyneuropathies in the differential diagnosis of patients with proximal muscle wasting associated with dropped head syndrome.

Mutational screening of the SH3TC2 gene in Greek patients with suspected demyelinating recessive Charcot-Marie-Tooth disease reveals a varied and unusual phenotypic spectrum.

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.

Charcot-Marie-Tooth disease type 4C in Norway: Clinical characteristics, mutation spectrum and minimum prevalence.

Autosomal recessive Charcot-Marie-Tooth disease (CMT) is considered rare and phenotypic descriptions are scarce for the different subgroups. Mutations in the SH3TC2 gene, causing recessive demyelinating CMT type 4C have been found in several Norwegian CMT patients over the last years. We aimed to estimate a minimum prevalence and to study the genotypic and phenotypic variability of CMT4C in Norway. Patients were selected from diagnostic registries in medical genetic centers in Norway for cases of CMT4C. All patients were invited to complete a questionnaire and give medical consent to the use of clinical data from medical hospital records. A total of 35 patients from 31 families were found with CMT4C, which gives a minimum prevalence of 0.7/100,000 in Norway. Six new mutations were identified. Most patients had debut in the first decade with foot deformities, distal limb paresis, sensory ataxia and scoliosis. Proximal lower limb paresis and cranial nerve involvement was seen in about half of the patients. CMT4C is the most common recessive CMT in Norway. In addition to the classic distal limb affection, early debut, scoliosis, proximal paresis, cranial nerve affection and sensory ataxia are the most prominent features of CMT4C.

Charcot-Marie-Tooth Disease type 4C: Novel mutations, clinical presentations, and diagnostic challenges.

INTRODUCTION: This study analyzes and describes atypical presentations of Charcot-Marie-Tooth disease type 4C (CMT4C). METHODS: We present clinical and physiologic features of 5 patients with CMT4C caused by biallelic private mutations of SH3TC2. RESULTS: All patients manifested scoliosis, and nerve conduction study indicated results in the demyelinating range. All patients exhibited signs of motor impairment within the first years of life. We describe 2 or more different genetic diseases in the same patient, atypical presentations of CMT, and 3 new mutations in CMT4C patients. DISCUSSION: A new era of unbiased genetic testing has led to this small case series of individuals with CMT4C and highlights the recognition of different genetic diseases in CMT4C patients for accurate diagnosis, genetic risk identification, and therapeutic intervention. The phenotype of CMT4C, in addition, appears to be enriched by a number of features unusual for the broad CMT category. Muscle Nerve 57: 749-755, 2018.

Phenotypic variability of CMT4C in a French-Canadian kindred.

INTRODUCTION: Charcot-Marie-Tooth type 4C (CMT4C) is an autosomal recessive dysmyelinating neuropathy characterized by precocious and rapidly progressive scoliosis. METHODS: Patients in a French-Canadian kindred were evaluated with clinical examination, electrophysiologic study, and genomic DNA extraction. RESULTS: Six of 10 siblings were clinically symptomatic with supportive electrophysiologic features. The proband presented with regional side-to-side sensorimotor asymmetry, typical pes cavus without obvious scoliosis, and unremarkable plain films of the spine. Affected siblings all share symptoms of foot deformity but have variable onset of neuropathic symptoms, degree of extremity weakness, progression of symptoms, and, most notably, evidence of scoliosis. DNA sequence analysis revealed a novel combination of 2 known recessive mutations, p.R904X and p.R954X, in the SH3TC2 gene. CONCLUSIONS: A broad spectrum of phenotypes should be considered in the possible diagnosis of CMT4C. The absence of scoliosis or late-onset symptoms should not exclude SH3TC2 from the list of candidate genes under consideration. Age of onset and clinical features were variable and suggest that polygenic factors contribute to the final phenotype.