Cancer Therapy-induced Dermatotoxicity as a Window to Understanding Skin Immunity.

Pruritus, rash, and various other forms of dermatotoxicity are the most frequent adverse events among patients with cancer receiving targeted molecular therapy and immunotherapy. Immune checkpoint inhibitors, macrophage-targeting agents, and epidermal growth factor receptor/MEK inhibitors not only exert antitumor effects but also interfere with molecular pathways essential for skin immune homeostasis. Studying cancer therapy-induced dermatotoxicity helps us identify molecular mechanisms governing skin immunity and deepen our understanding of human biology. This review summarizes new mechanistic insights emerging from the analysis of cutaneous adverse events and discusses knowledge gaps that remain to be closed by future research.

Myotonic dystrophy type 1 in South Korea: a comprehensive analysis of cancer and comorbidity risks.

BACKGROUND AND PURPOSE: Myotonic dystrophy type 1 (DM1) is an inherited neuromuscular disorder characterized by myotonia and progressive muscle weakness. Beyond the primary symptoms, there is growing concern regarding a higher incidence of certain comorbidities in DM1 patients, including cancer, diabetes, thyroid dysfunction, and cataracts. This study was designed to examine the occurrence of these conditions among patients diagnosed with DM1 in South Korea, using data from the National Health Insurance Service database. METHODS: The study undertook a comprehensive review of 3,842 patients diagnosed with DM1 between 2012 and 2018. We assessed the incidence of cancer and the prevalence of diabetes, thyroid dysfunction, and cataracts among these patients, comparing their rates to those in the general population. RESULTS: In the study cohort, 463 out of 3,842 DM1 patients (12.04%) were diagnosed with cancer, indicating a substantial elevation in cancer risk with an overall standard incidence ratio of 1.9 (95% CI = 1.6-2.3, p < 0.01) when compared to the expected rates in the general population. Moreover, the prevalence of diabetes (15.2%) and thyroid dysfunction (17.6%) was noteworthy in the DM1 population. The mean age at which DM1 patients underwent cataract surgery was 55.07 years, noticeably younger than the mean age of 69.25 years for cataract surgery in the general population. CONCLUSIONS: DM1 patients have a noteworthy occurrence of several comorbidities such as cancer, diabetes, thyroid dysfunction, and earlier cataract surgery. This highlights the importance of a comprehensive and integrative approach to the management and treatment of DM1, going beyond addressing only the primary neuromuscular symptoms. More research is required to understand the underlying mechanisms contributing to these comorbidities in DM1 patients, which may inform preventative measures and guide improvements in patient care.

The assessment of erectile dysfunction after radical prostatectomy using pudendal somatosensory evoked potential.

Erectile dysfunction in patients who underwent radical prostatectomy was evaluated with pudendal somatosensory evoked potentials (PSEP) to measure and predict erectile dysfunction objectively. Fifty-seven patients who completed requirements were included in the study. Patients were divided into 2 groups (potency/non-potency). Erectile function recovery was defined as question 2 and 3 on the IIEF-5 questionnaire at 12 months after surgery. The two-channel PSEP test was performed at the day before RP and 3-6 months after RP. Twenty patients were assigned to the potency group and 37 to the non-potency group. Mean age was less in the potency group. Other clinical variables were similar in two groups. The non-potency group had prolonged lumbar and cortical latencies in postoperative PSEP, and the mean differences of latencies between pre- and postoperative PSEP in lumbar and cortical regions were also greater in the non-potency group. Logistic regression analysis showed that age, lumbar post-operative latency, cortical post-operative latency, and difference of latency in lumbar region were associated with non-potency; odds ratios were 1.292 (p = 0.018), 0.425 (p = 0.047), 1.637 (p < 0.001), and 3.272 (p = 0.010), respectively. This study suggests that PSEP is an effective means of evaluating erectile dysfunction in prostate cancer patients after surgery.

Essential Thrombocythemia and Ischemic Stroke: A Case Series of Five JAK2-Positive Patients.

Background and Objectives: Essential thrombocythemia (ET) is a chronic myeloproliferative neoplasm characterized by elevated platelet counts and an increased risk of thrombotic events, including ischemic strokes. Materials and Methods: We conducted a retrospective analysis of data from consecutive ischemic stroke patients with ET between March 2014 and February 2023. Results: This case series describes the clinical presentation, radiological features, and management of five patients with ET-associated ischemic strokes, all harboring the JAK2 mutation. The diverse radiological findings suggest that both large and small vessel diseases may be influenced by the prothrombotic state induced by ET. A significant elevation in platelet count was observed to correlate with the emergence of new acute infarctions in some cases. Conclusions: The study highlights combined use of antiplatelet and cytoreductive therapy in preventing secondary stroke events in patients with ET and JAK2 mutations. The heterogeneity of stroke patterns in this population necessitates a comprehensive understanding of the underlying pathophysiological mechanisms and tailored therapeutic approaches.

Incidence and prevalence of Spinal and bulbar muscular atrophy in South Korea: a nationwide population-based study.

Spinal and bulbar muscular atrophy (SBMA), or Kennedy's disease, is a rare X-linked neuromuscular disorder predominantly affecting males and caused by a mutation in the androgen receptor gene. The epidemiology and comorbidities associated with SBMA in different ethnicities remain poorly understood. This study investigated the prevalence, incidence, and comorbidities associated with SBMA in the South Korean population using the Health Insurance Review and Assessment Service (HIRA) database. We retrospectively reviewed diagnosed cases of SBMA (G12.25 code of the Korean Classification of Diseases-7th edition) registered from January 1, 2016, to December 31, 2019, to calculate incidence and prevalence rates and concomitant comorbidities. Additionally, we surveyed SBMA patients (questionnaire group) visiting our clinic in 2022 to compare comorbidities with the HIRA data. The mean incidence rate of SBMA in the Korean population was 0.36/100,000 males from 2018 to 2019, while the prevalence rate was approximately 0.46/100,000 males from 2016 to 2019. The most common comorbidities identified in HIRA were gastritis and duodenitis (99.7%), gastroesophageal reflux (90.5%), hyperlipidemia (88.4%), and liver disorders (75.2%), which showed similar results in the questionnaire group. Additionally, gastric cancer was the most common type of cancer reported in SBMA in South Korea; although indeterminate, age-related factors may contribute to the development of cancer in these patients. Our findings provide valuable insights into the epidemiology and associated comorbidities of SBMA within the Korean population, which could inform clinical practice and future clinical research.

Characteristics of spinal and bulbar muscular atrophy in South Korea: a cross-sectional study of 157 patients.

Spinal and bulbar muscular atrophy, namely Kennedy disease, is a rare progressive neurodegenerative disorder caused by the expansion of a CAG repeat in the first exon of the androgen receptor gene on the X chromosome. We assessed the clinical history, laboratory findings, functional scales and electrophysiological data, as well as the levels of luteinizing hormone, follicle-stimulating hormone and testosterone, in 157 Korean patients with genetically confirmed spinal and bulbar muscular atrophy (mean age at data collection = 56.9 years; range = 33-83 years). Hand tremor was the first symptom noticed by patients at a median age of 35 years, followed by gynaecomastia, orofacial fasciculation, cramps and fatigability in ascending order. Clinical symptoms such as paraesthesia and dysphagia appeared during the later stages of the disease. Cane use during ambulation began at a median age of 62 years. There were statistically significant differences between patients and controls in the results of sensory nerve studies, motor conduction velocity, and distal latencies. Furthermore, among the hormone markers analysed, the level of luteinizing hormone exhibited a negative correlation with the spinal and bulbar muscular atrophy functional rating scale, Korean version. However, among the patients with a disease duration of ≤5 years, the levels of luteinizing hormone showed a significant correlation with assessments using the amyotrophic lateral sclerosis functional rating scale-revised, spinal and bulbar muscular atrophy functional rating scale, Korean version and the 6-minute walk test. In conclusion, our findings provide clinical information from a substantial number of patients with spinal and bulbar muscular atrophy in Korea that accorded with that of patients with this disease worldwide but with updated clinical features.

Epidemiological profile of myasthenia gravis in South Korea using the national health insurance database.

OBJECTIVES: Myasthenia gravis (MG) is an autoimmune disease characterized by muscle weakness and fatigue. Our objective was to investigate the incidence of MG using the National Health Insurance database of South Korea. MATERIALS AND METHODS: We conducted a retrospective cohort analysis of patients with the G70.0 code designated as MG and administered with MG medications for >3 months from 2007 to 2018 using nationwide data from South Korea. RESULTS: A total of 8,376 patients with MG during the period of 2010-2018 were identified. There were 3,862 (46.1%) male and 4,517 (53.9%) female patients. The standardized incidence rate was 1.18/100,000 in 2010, and increased to 1.81/100,000 in 2018. The standardized prevalence was 7.50/100,000 in 2010, and changed to 11.15/100,000 in 2018. Pyridostigmine was used to treat 82.3 ± 1.2% of patients with MG during 2010-2018. Among MG patients, 85.7 ± 0.9% used steroids, 31.6 ± 4.8% used azathioprine, 12.9 ± 9.5% used tacrolimus, 7.2 ± 2.1% used cyclosporine, 6.2 ± 1.8% used mycophenolate mofetil, and 0.4 ± 0.1% used methotrexate. Thymectomy was performed in 1,130 MG patients, and the time from MG diagnosis to thymectomy decreased from 2010 to 2018. CONCLUSION: Based on the national registry data from 2010 to 2018, the incidence and prevalence rate in South Korea has increased. Whereas the use of IVIG has remained stable, thymectomy is performed earlier than before, and the distribution of immunosuppressant therapies has changed over the years with an increase in tacrolimus and mycophenolate mofetil. We expect that this study will serve as a basis for future South Korean MG epidemiological studies.

Multiorgan Signaling Mobilizes Tumor-Associated Erythroid Cells Expressing Immune Checkpoint Molecules.

Hematopoietic-derived cells are integral components of the tumor microenvironment and serve as critical mediators of tumor-host interactions. Host cells derived from myeloid and lymphoid lineages perform well-established functions linked to cancer development, progression, and response to therapy. It is unclear whether host erythroid cells also contribute to shaping the path that cancer can take, but emerging evidence points to this possibility. Here, we show that tumor-promoting environmental stress and tumor-induced hemodynamic changes trigger renal erythropoietin production and erythropoietin-dependent expansion of splenic erythroid cell populations in mice. These erythroid cells display molecular features indicative of an immature erythroid phenotype, such as the expression of both CD71 and TER119 and the retention of intact nuclei, and express genes encoding immune checkpoint molecules. Nucleated erythroid cells with similar properties are present in mouse and human tumor tissues. Antibody-mediated erythropoietin blockade reduces tumor-responsive erythroid cell induction and tumor growth. These findings reveal the potential of tumor-induced erythropoietin and erythroid cells as targets for cancer treatment. IMPLICATIONS: : Our study identifies erythropoietin and erythroid cells as novel players in tumor-host interactions and highlights the involvement of multiorgan signaling events in their induction in response to environmental stress and tumor growth.

Intracellular signaling modules linking DNA damage to secretome changes in senescent melanoma cells.

Cellular senescence is a major barricade on the path of cancer development, yet proteins secreted from senescent cells exert complex and often discordant effects on subsequent cancer evolution. Somatic genome alternations driving the formation of nevi and melanoma are efficient inducers of cellular senescence. Melanocyte and melanoma cell senescence is likely to come into play as a key factor affecting the course of tumorigenesis and responsiveness to therapy; little mechanistic information has been generated, however, that substantiates this idea and facilitates its clinical translation. Here, we established and characterized a model of melanoma cell senescence in which pharmacologically induced DNA damage triggered divergent ATM kinase- and STING-dependent intracellular signaling cascades and resulted in cell cycle arrest, cytomorphologic remodeling, and drastic secretome changes. Targeted proteome profiling revealed that senescent melanoma cells in this model secreted a panoply of proteins shaping the tumor immune microenvironment. CRISPR-mediated genetic ablation of the p38α and IKKß signaling modules downstream of the ATM kinase severed the link between DNA damage and this secretory phenotype without restoring proliferative capacity. A similar genetic dissection showed that loss of STING signaling prevented type I interferon induction in DNA-damaged melanoma cells but otherwise left the senescence-associated processes in our model intact. Actionable proteins secreted from senescent melanoma cells or involved in senescence-associated intracellular signaling hold potential as markers for melanoma characterization and targets for melanoma treatment.

Under-recognized primary spontaneous pneumothorax in ALS: a multicenter retrospective study.

Primary spontaneous pneumothorax (PSP) is not an uncommon disease, especially in patients with risk factors such as male gender, history of smoking, and low body mass index (BMI). Amyotrophic lateral sclerosis (ALS) is a rare disease caused by neurodegeneration of the motor neurons that share risk factors with PSP. The aim of this study was to determine the prevalence of PSP in ALS and find the significant risk factors related to PSP. We retrospectively reviewed the data from 86 patients with clinically probable or definite ALS from three different centers. Clinical characteristics, including age, sex, subtype, disease duration, body mass index, history of smoking, tracheostomy state, and ventilator use, were obtained. The ALS Functional Rating Scale-Revised Form (ALSFRS-R) total score and subscores were also retrieved from the medical records. In the results, six of the 86 patients (7%) had PSP. There were no statistically significant differences among the clinical characteristics and the ALSFRS-R scores between the patients with and without PSP, except for BMI and smoking (p < 0.022 and p < 0.019, respectively). A multivariate logistic regression analysis of smoking and BMI showed an odds ratio of 19.25. In conclusion, the existence of PSP in ALS may be under-recognized. Further well-designed, large studies are needed to elucidate the prevalence and pathophysiology of pneumothorax in ALS.

The protein kinase p38α destabilizes p63 to limit epidermal stem cell frequency and tumorigenic potential.

The molecular circuitry directing tissue development and homeostasis is hardwired by genetic programs but may also be subject to fine-tuning or major modification by environmental conditions. It remains unclear whether such malleability is at work-particularly in tissues directly in contact with the environment-and contributes to their optimal maintenance and resilience. The protein kinase p38α is activated by physiological cues that signal tissue damage and neoplastic transformation. Here, we found that p38α phosphorylated and thereby destabilized p63, a transcription factor essential for epidermal development. Through this regulatory mechanism, p38α limited the frequency of keratinocytes with stem cell properties and tumorigenic potential. Correspondingly, epidermal loss of p38α expression or activity promoted or correlated with carcinogenesis in mouse and human skin, respectively. Genetic mouse models revealed a tumorigenic mechanism from p38α loss through p63-mediated suppression of the matrix metalloprotease MMP13. These findings illustrate a previously uncharacterized epidermal tumor-suppressive mechanism in which stress-activated signaling induces the contraction of stem cell-like keratinocyte pools.

Selenoprotein MsrB1 promotes anti-inflammatory cytokine gene expression in macrophages and controls immune response in vivo.

Post-translational redox modification of methionine residues often triggers a change in protein function. Emerging evidence points to this reversible protein modification being an important regulatory mechanism under various physiological conditions. Reduction of oxidized methionine residues is catalyzed by methionine sulfoxide reductases (Msrs). Here, we show that one of these enzymes, a selenium-containing MsrB1, is highly expressed in immune-activated macrophages and contributes to shaping cellular and organismal immune responses. In particular, lipopolysaccharide (LPS) induces expression of MsrB1, but not other Msrs. Genetic ablation of MsrB1 did not preclude LPS-induced intracellular signaling in macrophages, but resulted in attenuated induction of anti-inflammatory cytokines, such as interleukin (IL)-10 and the IL-1 receptor antagonist. This anomaly was associated with excessive pro-inflammatory cytokine production as well as an increase in acute tissue inflammation in mice. Together, our findings suggest that MsrB1 controls immune responses by promoting anti-inflammatory cytokine expression in macrophages. MsrB1-dependent reduction of oxidized methionine in proteins may be a heretofore unrecognized regulatory event underlying immunity and inflammatory disease, and a novel target for clinical applications.

Epithelial Control of Gut-Associated Lymphoid Tissue Formation through p38α-Dependent Restraint of NF-κB Signaling.

The protein kinase p38α mediates cellular responses to environmental and endogenous cues that direct tissue homeostasis and immune responses. Studies of mice lacking p38α in several different cell types have demonstrated that p38α signaling is essential to maintaining the proliferation-differentiation balance in developing and steady-state tissues. The mechanisms underlying these roles involve cell-autonomous control of signaling and gene expression by p38α. In this study, we show that p38α regulates gut-associated lymphoid tissue (GALT) formation in a noncell-autonomous manner. From an investigation of mice with intestinal epithelial cell-specific deletion of the p38α gene, we find that p38α serves to limit NF-κB signaling and thereby attenuate GALT-promoting chemokine expression in the intestinal epithelium. Loss of this regulation results in GALT hyperplasia and, in some animals, mucosa-associated B cell lymphoma. These anomalies occur independently of luminal microbial stimuli and are most likely driven by direct epithelial-lymphoid interactions. Our study illustrates a novel p38α-dependent mechanism preventing excessive generation of epithelial-derived signals that drive lymphoid tissue overgrowth and malignancy.

p38α MAPK is required for tooth morphogenesis and enamel secretion.

An improved understanding of the molecular pathways that drive tooth morphogenesis and enamel secretion is needed to generate teeth from organ cultures for therapeutic implantation or to determine the pathogenesis of primary disorders of dentition (Abdollah, S., Macias-Silva, M., Tsukazaki, T., Hayashi, H., Attisano, L., and Wrana, J. L. (1997) J. Biol. Chem. 272, 27678-27685). Here we present a novel ectodermal dysplasia phenotype associated with conditional deletion of p38α MAPK in ectodermal appendages using K14-cre mice (p38α(K14) mice). These mice display impaired patterning of dental cusps and a profound defect in the production and biomechanical strength of dental enamel because of defects in ameloblast differentiation and activity. In the absence of p38α, expression of amelogenin and ß4-integrin in ameloblasts and p21 in the enamel knot was significantly reduced. Mice lacking the MAP2K MKK6, but not mice lacking MAP2K MKK3, also show the enamel defects, implying that MKK6 functions as an upstream kinase of p38α in ectodermal appendages. Lastly, stimulation with BMP2/7 in both explant culture and an ameloblast cell line confirm that p38α functions downstream of BMPs in this context. Thus, BMP-induced activation of the p38α MAPK pathway is critical for the morphogenesis of tooth cusps and the secretion of dental enamel.

Recessive C10orf2 mutations in a family with infantile-onset spinocerebellar ataxia, sensorimotor polyneuropathy, and myopathy.

Recessive mutations in chromosome 10 open reading frame 2 (C10orf2) are relevant in infantile-onset spinocerebellar ataxia (IOSCA). In this study, we investigated the causative mutation in a Korean family with combined phenotypes of IOSCA, sensorimotor polyneuropathy, and myopathy. We investigated recessive mutations in a Korean family with two individuals affected by IOSCA. Causative mutations were investigated using whole exome sequencing. Electrophysiological analyses and muscle and nerve biopsies were performed, along with magnetic resonance imaging (MRI) of the brain and lower extremities. Compound heterozygous mutations c.1460C>T and c.1485-1G>A in C10orf2 were identified as causative of IOSCA. Skeletal muscle showed mitochondrial DNA (mtDNA) deletions. Both patients showed a period of normal development until 12-15 months, followed by ataxia, athetosis, hearing loss, and intellectual disability. Electrophysiological findings indicated motor and sensory polyneuropathies. Muscle biopsy revealed variations in the size and shape of myofibers with scattered, small, and angulated degenerating myofibers containing abnormal mitochondria; these observations are consistent with myopathy and may be the result of mtDNA deletions. Sural nerve biopsy revealed an axonal neuropathy. High-signal-intensity lesions in the middle cerebellar peduncles were correlated with clinical severity, and MRI of the lower legs was compatible with the hypothesis of length-dependent axonal degeneration. We identified novel compound heterozygous mutations of the C10orf2 gene as the cause of IOSCA with sensorimotor polyneuropathy and myopathy. Signs of motor neuropathy and myopathy were discovered for the first time in IOSCA patients with C10orf2 mutations. These results suggest that the clinical spectrum of IOSCA caused by C10orf2 mutations may be more variable than previously reported.

Loss of epidermal p38α signaling prevents UVR-induced inflammation via acute and chronic mechanisms.

UVB is a component of solar radiation primarily responsible for causing damage and cancer in irradiated skin, and disrupting immune homeostasis. The immediate harm and long-term health risks of excessive sunlight exposure are affecting the lives of nearly all people worldwide. Inflammation is a key mechanism underlying UVB's various detrimental effects. Here we show that activation of the protein kinase p38α is restricted to the epidermis in UVB-exposed skin, and that p38α ablation targeted to the epithelial compartment is sufficient to suppress UVB-induced inflammation. Mechanistically, loss of epithelial p38α signaling attenuates the expression of genes required to induce vascular leakage and edema, and also increases the steady-state abundance of epidermal γδ T cells, which are known to promote the repair of damaged epidermis. These effects of p38α deficiency delineate a molecular network operating at the organism-environment interface, and reveal conditions crucial to preventing the pathology resulting from sun-damaged skin.

Exome Sequencing Reveals a Novel PRPS1 Mutation in a Family with CMTX5 without Optic Atrophy.

BACKGROUND: X-linked Charcot-Marie-Tooth disease type 5 (CMTX5) is caused by mutations in the gene encoding phosphoribosyl pyrophosphate synthetase I (PRPS1). There has been only one case report of CMTX5 patients. The aim of this study was to identify the causative gene in a family with CMTX with peripheral neuropathy and deafness. CASE REPORT: A Korean family with X-linked recessive CMT was enrolled. The age at the onset of hearing loss of the male proband was 5 months, and that of steppage gait was 6 years; he underwent cochlear surgery at the age of 12 years. In contrast to what was reported for the first patients with CMTX5, this patient did not exhibit optic atrophy. Furthermore, there was no cognitive impairment, respiratory dysfunction, or visual disturbance. Assessment of his family history revealed two male relatives with very similar clinical manifestations. Electrophysiological evaluations disclosed sensorineural hearing loss and peripheral neuropathy. Whole-exome sequencing identified a novel p.Ala121Gly (c.362C>G) PRPS1 mutation as the underlying genetic cause of the clinical phenotype. CONCLUSIONS: A novel mutation of PRPS1 was identified in a CMTX5 family in which the proband had a phenotype of peripheral neuropathy with early-onset hearing loss, but no optic atrophy. The findings of this study will expand the clinical spectrum of X-linked recessive CMT and will be useful for the molecular diagnosis of clinically heterogeneous peripheral neuropathies.

Tuning of protein kinase circuitry by p38α is vital for epithelial tissue homeostasis.

The epithelium of mucosal and skin surfaces serves as a permeability barrier and affords mechanisms for local immune defense. Crucial to the development and maintenance of a properly functioning epithelium is the balance of cell proliferation, differentiation, and death. Here we show that this balance depends on cross-regulatory interactions among multiple protein kinase-mediated signals and their coordinated transmission. From an investigation of conditional gene knock-out mice, we find that epithelial-specific loss of the protein kinase p38α leads to aberrant activation of TAK1, JNK, EGF receptor, and ERK in distinct microanatomical areas of the intestines and skin. Consequently, the epithelial tissues display excessive proliferation, inadequate differentiation, and sensitivity to apoptosis. These anomalies leave the tissue prone to damage and collapse at the trigger of an environmental insult. The vulnerability of p38α-deficient epithelium predicts adverse effects of long term pharmacological p38α inhibition; yet such limitations could be overcome by concomitant blockade of one or more of the dysregulated protein kinase signaling pathways.

Mutations in the PLEKHG5 gene is relevant with autosomal recessive intermediate Charcot-Marie-Tooth disease.

BACKGROUND: Mutations in the Pleckstrin homology domain-containing, family G member 5 (PLEKHG5) gene has been reported in a family harboring an autosomal recessive lower motor neuron disease (LMND). However, the PLEKHG5 mutation has not been described to cause Charcot-Marie-Tooth disease (CMT). METHODS: To identify the causative mutation in an autosomal recessive intermediate CMT (RI-CMT) family with childhood onset, whole exome sequencing (WES), histopathology, and lower leg MRIs were performed. Expression and activity of each mutant protein were analyzed. RESULTS: We identified novel compound heterozygous (p.Thr663Met and p.Gly820Arg) mutations in the PLEKHG5 gene in the present family. The patient revealed clinical manifestations of sensory neuropathy. Fatty replacements in the distal lower leg muscles were more severe than in the thigh muscles. Although the symptoms and signs of this patient harboring slow nerve conduction velocities suggested the possibility of demyelinating neuropathy, a distal sural nerve biopsy was compatible with axonal neuropathy. Immunohistochemical analysis revealed that the patient has a low level of PLEKHG5 in the distal sural nerve and an in vitro assay suggested that the mutant proteins have a defect in activating the NF-κB signaling pathway. CONCLUSIONS: This study identifies compound heterozygous PLEKHG5 mutations as the cause of RI-CMT. We suggest that PLEKHG5 might play a role in the peripheral motor and sensory nervous system. This study expands the phenotypic spectrum of PLEKHG5 mutations.