Background and purpose Charcot‐Marie‐Tooth (CMT) disease is a chronic, slowly progressing disorder. The lack of specific disease progression biomarkers limits the execution of clinical trials. However, neurofilament light chain (NfL) has been suggested as a potential biomarker for peripheral nervous system disorders. Methods Ninety‐six CMT disease patients and 60 healthy controls were enrolled in the study. Disease severity assessment included clinical evaluation with CMT Neuropathy Score version 2 (CMTNSv2). Blood plasma NfL concentrations were measured using the single‐molecule array NfL assay. Results The NfL concentration was significantly higher in the CMT disease patient group than in the controls (p < 0.001). Of the CMT disease patients, those with type CMTX1 had a higher NfL level than those in the two other analysed subgroups (CMT1A and other CMT disease types) (p = 0.0498). The NfL concentration had a significant but weak correlation with the CMTNSv2 (rs = 0.25, p = 0.012). In one CMT disease patient with an extremely elevated NfL level, overlap with chronic inflammatory demyelinating polyneuropathy was suspected. Receiver operating characteristic analysis showed that an NfL concentration of 8.9 pg/ml could be used to discriminate CMT disease patients from controls, with an area under the curve of 0.881. Conclusions Our study confirmed that the plasma NfL concentration is significantly higher in CMT disease patients than in controls. Plasma NfL concentration was found to significantly, albeit weakly, reflect the clinical severity of CMT disease. In the future, NfL may be used, either individually or collaboratively, as a biomarker in the clinical context of suspected CMT disease; however, several issues need to be addressed first.

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Background: Spinal and bulbar muscular atrophy (SBMA) or Kennedy disease [OMIM: 313200] is a rare X-linked neuromuscular disease. Patients commonly present with muscle cramps, tremors, leg weakness, dysarthria and dysphagia.Methods: We deeply phenotyped and evaluated the possible extent of affected systems in all patients with SBMA in Latvia (n = 5). In addition, neurophysiological studies and blood analyses were used to perform a molecular diagnosis and evaluate biochemical values. We analyzed neurofilament light (NfL) as a possible biomarker.Results: Neurological examination revealed typical SBMA clinical manifestations; all patients had small or large nerve fiber neuropathy. Three of five patients had increased neurofilament light levels.Conclusion: The study confirms the systemic involvement in patients suffering from SBMA. Increased NfL concentration was associated with either peripheral neuropathy or decreased body mass index. The complex phenotype of the disease should be kept in mind, as it could help to diagnose patients with SBMA.

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Peripheral neuropathy is a disorder of the peripheral nerves and results from a disturbance of structure and/or function of the peripheral sensory, motor and/or autonomic neurons. The possible aetiology of peripheral neuropathies is diverse, but inflammatory and hereditary diseases of the peripheral nerves predominate in childhood. The aim of this study was to determine the clinical and electrophysiological profile of large nerve fibre neuropathy detected by nerve conduction studies (NCS) in children over a 10-year period at the Children's Clinical University Hospital in Latvia. Based on NCS findings, 165 children between 2008 and 2018 were diagnosed with polyneuropathy. In our study, the majority of children had peripheral neuropathy due to acquired causes, mostly due to diabetes mellitus; roughly one in five of the patients had hereditary neuropathy. Almost half of the patients had motor deficits, which were more prevalent in toxic and inflammatory neuropathies. A little less than a third of patients complained of pain as well as presenting with autonomic dysfunction symptoms. The NCS demonstrated a demyelinating neuropathy in 52 cases (31%), an axonal neuropathy in 34 cases (21%), and mixed polyneuropathy in 79 cases (48%).Our study investigated the clinical and electrophysiological characteristics of polyneuropathies diagnosed with NCS in children. Most of the polyneuropathies in our study were hereditary and diabetic neuropathies with combined (myelin and axon) damage to nerve fibres. Almost all clinical symptoms of polyneuropathy were present in all aetiological groups.

X-linked Charcot-Marie-Tooth (CMT) disease type I (CMTX1) is the second most frequent type of CMT disease caused by pathogenic variants in the <i>GJB1</i> gene. We described 2 extended cases (families) with CMTX1 with identified pathogenic variants – p.Val139Met and p.Arg215Trp. In both the families, neurological symptoms started earlier in male than in female patients. In some family members, molecular diagnostics was performed prior to neurological investigation due to family cascade screening. There was variable neurological phenotype representing CMT. Conclusions: There is a large clinical heterogeneity in CMTX, even amongst the family members.

Background: Kennedy disease or spinal and bulbar muscular atrophy (SBMA) is a rare X-linked neuromuscular disease. Patients commonly present with muscle cramps, tremor, leg weakness, dysarthria, and dysphagia. Methods: We deeply phenotyped and evaluated the possible extent of affected systems in all Kennedy disease patients in Latvia (n = 5), neurophysiological studies, blood analysis was used in order to carry out molecular diagnosis and evaluate biochemical values. We analysed neurofilament light as possible biomarker. Results: Neurological examination revealed typical manifestations of lower-motor neuron damage; two patients had polyneuropathy. Quantitative sensory testing revealed tactile threshold abnormalities and perception of mechanical pain in all patients. Three of five patients had increased neurofilament light levels. Conclusion: Study confirms the systemic involvement in patients suffering from Kennedy disease. Increased NfL concentration was associated with either peripheral neuropathy or decreased body mass index. The complex phenotype of the disease should be kept in mind as it could help to diagnose patients with SBMA.

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