Clinicopathological features in two families with MARS-related Charcot-Marie-Tooth disease.

Mutations in MARS gene cause dominant Charcot-Marie-Tooth disease (CMT) 2U. The aim of this study is to investigate phenotypic heterogeneities and peripheral neuropathology of MARS-related CMT patients. We identified a heterozygous p. R199Q mutation and an already reported heterozygous p. P800T mutation of MARS gene in two unrelated families using targeted next-generation sequencing. The first pedigree comprised three patients over three generations and the second pedigree comprised two patients over two generations. In addition of an asymptomatic carrier in the second pedigree, all patients presented with childhood-onset length dependent sensorimotor neuropathy with pes cavus. Nerve conduction studies revealed slowing of motor nerve conduction velocities (MNCV) of the median nerve indicating intermediate neuropathy in the patient with the p. R199Q mutation, and normal MNCV with reduced compound muscle action potential indicating axonal neuropathy in the patient with the p. P800T mutation. Magnetic resonance imaging detected a pattern of nerve changes similar to those in demyelinating polyneuropathies in intermediate type (p. R199Q mutation) patients compared with normal in the axonal type (p. P800T mutation) patients. Additionally, sural nerve biopsy revealed loss of myelinated axons with onion bulb formation in both mutations. By electron microscopy, a marked decrease of myelinated and unmyelinated fiber, neurofilaments aggregate with degenerating mitochondria and microtubule loss in axons were frequently found. Denervated Schwann cell complexes and few collagen pockets indicated involvement of unmyelinated Schwann cells. Therefore, the investigated MARS mutations cause not only the known axonal type but also intermediate type neuropathy with involvement of both axons and Schwann cells. Those findings are useful for the differential diagnosis of CMT patients with unknown MARS variants.

Sural biopsy to detect the axonal cytoskeleton defects in KIF5A-related Charcot-Marie-Tooth disease type 2.

Kinesins are microtubule-associated motor proteins involved in in regulating microtubule dynamics in neuronal and non-neuronal cells. However, the axonal cytoskeleton-related pathological changes in peripheral nerve have never been described in patients with KIF5A mutation. This study aims to report sural biopsy to detect axonal cytoskeleton abnormalities in a patient with KIF5A-related Charcot-Marie-Tooth disease type 2 (CMT2). We screened for the variants of CMT or related pathogenic genes using next-generation sequencing in a Chinese family with CMT2. The proband was a 13-year-old girl who presented with severe weakness and wasting of distal muscles of limbs starting at early childhood. The disease rapidly progressed, and the girl lost ambulation. Her mother showed absence of deep tendon reflexes in the lower limbs. Nerve conduction studies disclosed a more pronounced axonal sensory-motor neuropathy in the proband. The girl and her mother had a heterozygous p.E755K mutation of the KIF5A gene, which was previously reported only in hereditary spastic paraplegia and amyotrophic lateral sclerosis. Sural biopsy revealed loss of both myelinated and unmyelinated nerve fibers. Closely packed, irregularly oriented neurofilaments were observed in axons of unmyelinated nerve fibers. Another important finding was ubiquitous presence of elongated mitochondria with vacuole in the myelinated and unmyelinated axons. This study suggested the p.E755K mutation of KIF5A was a cause of early-onset CMT2 with defective axonal transport, and emphasized sural biopsy could be an important tool to detect axonal cytoskeleton defects in KIF5A related CMT2.

PLEKHG5-related autosomal recessive lower motor neuron disease with dysmyelination in peripheral nerves.

OBJECTIVE: Pleckstrin homology domain-containing family G member 5 (PLEKHG5) is a nuclear factor-κ-B-activator gene that predominantly expresses in the neurons and Schwann cells of the peripheral nervous system. Variations in the PLEKHG5 have shown an intermediate form of autosomal recessive Charcot-Marie-Tooth disease and lower motor neuron disease in childhood. MATERIALS AND METHODS: This study investigated clinically, electrophysiologically, genetically, and pathologically a young girl with lower motor neuron disease who had weakness and wasting of all limbs starting in early childhood. RESULTS: Next-generation sequencing found a novel compound heterozygous missense variation c.2038-1G>A and c.1219G>T of PLEKHG5 gene. Electromyography revealed a neurogenic pattern, and nerve conduction study indicated subclinical sensory neuropathy. Sural biopsy showed hypomyelination, hypermyelination, and infolding myelin membranes coiled into the myelinated axon. CONCLUSION: This study identifies, pathologically, novel compound heterozygous mutations and phenotype in PLEKHG5-related lower motor neuron disease and dysmyelination in a patient with PLEKHG5 mutation.

A novel mutation in PRPS1 causes X-linked Charcot-Marie-Tooth disease-5.

X-linked Charcot-Marie-Tooth disease-5 (CMTX5) is a rare hereditary disorder caused by mutations in the gene for phosphoribosyl pyrophosphate synthetase-1 (PRPS1). We investigated a boy with a novel PRPS1 mutation (c.334G>C, p.V112L) via genetic, neuropathological and enzymatic tests. The proband was a 13-year-old boy with congenital non-syndromic sensorineural deafness. At 3 year old, he developed progressive distal weakness of all limbs with muscle atrophy of both hands and shanks. Nerve conduction study revealed the loss of sensory nerve action potentials, and slowing down of motor nerve conduction velocities with a decrease of amplitudes of compound motor action potentials. Visual evoked potentials and brainstem auditory evoked potentials were not bilaterally evocable. Sural biopsy proved the loss of myelinated nerve fibers, with axonal degeneration, regenerating clusters and onion bulbs. Enzymatically, PRPS1 activity was close to zero in the proband and mildly reduced in his mother, compared with controls. To our knowledge, this is the first report of CMTX5 in a Chinese population. The genetic finding has expanded the genotypic spectrum of PRPS1 mutations.

HADHB mutations cause infantile-onset axonal Charcot-Marie-Tooth disease: A report of two cases.

Mitochondrial trifunctional protein deficiency (MTPD) is a rare disorder caused by mutations in the HADHA and HADHB genes. Here, we report on two Han Chinese patients with HADHB mutation-associated infantile axonal Charcot-Marie-Tooth disease (IACMT). Both patients were unrelated. Case 1 was a 19-year-old man, and case 2 was a 5-year-old boy. Both had delayed motor development and slowly-progressing distal muscle weakness with areflexia and foot deformities. The electrophysiology findings were compatible with axonal polyneuropathy in both patients. Blood tandem mass spectrometry showed increased concentrations of multiple acylcarnitines. Nerve biopsies showed axonal neuropathy with a moderate loss of myelinated fibers. Gene analysis identified two compound heterozygous mutations (c.184A>G/c.340A>G and c.488G>A/c.1175C>T, respectively) in the HADHB gene. The c.488G>A mutation was novel. This study broadens the phenotype of MTPD and suggests that the genetic testing of patients suffering from IACMT should include the HADHB gene.
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Late-onset hereditary sensory and autonomic neuropathy expands the phenotypic spectrum of MFN2-related diseases.

Mutations in the Mitofusin 2 (MFN2) gene have been identified in patients with autosomal dominant axonal motor and sensory neuropathy or Charcot-Marie-Tooth 2A (CMT2A). Here we describe clinical and pathological changes in an adult patient with sporadic hereditary sensory and autonomic neuropathy (HSAN) due to an MFN2 mutation. The patient was a 53-year-old man who had sensory involvement and anhidrosis in all limbs without motor features. The electrophysiological assessment documented severe axonal sensory neuropathy. The sural nerve biopsy confirmed the electrophysiological findings, revealing severe loss of myelinated and unmyelinated fibers with regeneration clusters. Genetic analysis revealed the previously identified mutation c.776 G > A in MFN2. Our report expands the phenotypic spectrum of MFN2-related diseases. Sequencing of MFN2 should be considered in all patients presenting with late-onset HSAN.

Adult-onset demyelinating neuropathy associated with FBLN5 gene mutation.

Rare forms of autosomal-dominant Charcot-Marie-Tooth disease (AD-CMT) may be associated with mutations in Fibulin-5 (FBLN5) as AD-CMT is genetically heterogeneous. Here, we report the first pathological study of an Asian family. The proband was a 46-year-old man with slowly progressive distal numbness and weakness for 12 years. He had a history of diabetes mellitus for 12 years. His mother was 81 years old and had mild polyneuropathy. His 16-year-old daughter was asymptomatic. The nerve conduction velocities (NCVs) and compound muscular action potential (CMAP) amplitudes were moderately to severely reduced in the proband, and moderately reduced in his daughter and mother. A sensory response could not be elicited in the proband and was moderately to severely decreased in the daughter and mother. Nerve ultrasound indicated a general enlargement of the peripheral nerves in the proband, daughter, and mother. A sural nerve biopsy from the proband demonstrated a pronounced depletion of myelinated fibers, thin myelinated fibers, and onion-bulb formations. A reported heterozygous mutation of c.1117C>T in FBLN5 was identified in the proband, mother, and daughter. These findings confirm a novel subtype of AD-CMT 1 due to a mutation in the FBLN5 gene.
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INF2 mutations associated with dominant inherited intermediate Charcot-Marie-Tooth neuropathy with focal segmental glomerulosclerosis in two Chinese patients.

Recently, mutations in the inverted formin 2 (INF2) gene have been indentified in patients with dominant inherited intermediate Charcot-Marie-Tooth neuropathy (DI-CMT) with focal segmental glomerulosclerosis (FSGS). We report clinical and nerve pathological changes in two Chinese patients. Case 1 is 27 years old and presented with distal muscle weakness and atrophy of legs at the age of 13 and renal failure at the age of 26. Three of his family members died due to pure renal failure. Case 2 is 22 years old and presented with distal muscle weakness and atrophy of the legs with transient attacks of difficulty in speaking at age 17. Proteinuria was found by routine urine test at the same time. Sural nerve biopsy revealed moderate-to-severe loss of myelinated fibers with union bulbs and regeneration clusters in both patients. Ultrastructurally, numerous elongated extensions of Schwann cells of unmyelinated fibers could be seen in both patients. INF2 gene mutation screening revealed c.451 T>C in case 1 and c.341 G>A in case 2. This is the first report of Chinese patients with INF2-related DI-CMT. The c.451 T>C mutant was responsible for both isolated FSGS and a dual phenotype of FSGS and neuropathy within one family. Intrafamilial variability can be found with the same INF2 mutation. The CNS manifestations further broadened the clinical spectrum of INF2- associated disorders.

Mitofusin 2 gene mutation causing early-onset CMT2A with different progressive courses.

Charcot-Marie-Tooth disease Type 2A2 (CMT2A2), caused by mitofusin 2 (MFN2) genes, has been clinically classified into two types: severe early-onset and mild benign. Here we reported 3 early onset patients with different progressive courses. The 3 patients had mutations R94W, R364W and a novel W740R in the MFN2 gene. Two patients presented with progressive distal limb muscle weakness and wasting from the ages of 5 and 6 years, respectively. The disease developed slowly, with loss of ambulation after 35 years of age. The third patient presented with similar symptoms after birth, and has never been able to walk independently. Sural nerve biopsies revealed severe axonal neuropathy with mitochondrial aggregation in axons. Our data confirmed that early-onset CMT2A2 can present with different courses in Chinese patients. The novel mutation in MFN2 found in this study broadens the genotypic spectrum associated with MFN2 related CMT.

Pathogenic PSAT1 Variants and Autosomal Recessive Axonal Charcot-Marie-Tooth Disease With Ichthyosis.

BACKGROUND: Biallelic pathogenic phosphoserine aminotransferase 1 (PSAT1) variants generally cause a severe phenotype predominantly involving the central nervous system. Here, for the first time, we report two patients harboring pathogenic PSAT1 variants only manifested as polyneuropathy and ichthyosis. METHODS: Two patients from unrelated families presenting with polyneuropathy and ichthyosis were enrolled. Whole exome sequencing was performed to identify possible disease-causing variants. Their clinical, electrophysiological, imaging, biochemical, and pathologic changes were in detail assessed and investigated. RESULTS: Homozygous variant c.43G>C and compound heterozygous variants c.112A>C and c.43G>C in PSAT1 were identified in patients 1 and 2, respectively. Nerve conduction studies revealed preserved or mild slowing motor nerve conduction velocities of the median nerves in the two patients, whereas the compound motor action potential in patient 1 was severely decreased. Brain magnetic resonance imaging of the two patients found no abnormalities. Median nerve enlargement was observed on ultrasound in patient 1. Both patients had normal level of serine and glycine in plasma and cerebrospinal fluid. Sural nerve biopsy found severe loss of myelinated fibers. Electron microscopy revealed neurofilament accumulation and mitochondrial aggregation in axons. Both variants in PSAT1 were classified as likely pathogenic or pathogenic variants according to the standard guidelines. CONCLUSIONS: Our study confirms that pathogenic PSAT1 variants can cause a mild phenotype, predominantly as autosomal recessive axonal Charcot-Marie-Tooth disease.

The Pathological Features of Common Hereditary Mitochondrial Dynamics Neuropathy.

OBJECTIVES: Mitofusin 2 and ganglioside-induced differentiation-associated protein 1 are two main mitochondrial dynamics-related proteins. Dysfunction of these two proteins leads to different subtypes of Charcot-Marie-Tooth disease type 2A (CMT2A) and CMT2K. This study aims to report the pathological difference between CMT2A and CMT2K in a large cohort. METHODS: Thirty patients with molecularly confirmed CMT2A and nine with CMT2K were identified by next-generation sequencing. Sural nerve biopsies were performed in 29 patients. RESULTS: The patients with both diseases showed length-dependent neuropathy with distal weakness, sensory loss, and no deep tendon reflex. Optic neuropathy appeared in 3/30 (10%) patients with CMT2A. Tendon contracture appeared in 4/9 (50.0%) patients with CMT2K. Sural biopsy revealed the loss of both myelinated and unmyelinated nerve fibers. Closely packed, irregularly oriented neurofilaments were observed in axons of unmyelinated nerve fibers in both diseases. Another important finding was the ubiquitous presence of smaller, rounded, and fragmented mitochondria in CMT2A and elongated mitochondria in CMT2K in the myelinated and unmyelinated axons. CONCLUSION: This study confirmed large diversity in phenotypes between CMT2A and CMT2K. Mitochondrial dynamics-related variations can induce different mitochondrial morphological changes and neurofilament accumulation in axons.

Facile Synthesis of Highly Dispersed Co3O4 Nanoparticles on Expanded, Thin Black Phosphorus for a ppb-Level NO x Gas Sensor.

Expanded few-layer black phosphorus nanosheets (FL-BP NSs) were functionalized by branched polyethylenimine (PEI) using a simple noncovalent assembly to form air-stable overlayers (BP-PEI), and a Co3O4@BP-PEI composite was designed and synthesized using a hydrothermal method. The size of the highly dispersed Co3O4 nanoparticles (NPs) on the FL-BP NSs can be controlled. The BP-C5 (190 °C for 5 h) sensor, with 4-6 nm Co3O4 NPs on the FL-BP NSs, exhibited an ultrahigh sensitivity of 8.38 and a fast response of 0.67 s to 100 ppm of NO x at room temperature in air, which is 4 times faster than the response of the FL-BP NS sensor, and the lower detection limit reached 10 ppb. This study points to a promising method for tuning properties of BP-based composites by forming air-stable overlayers and highly dispersed metal oxide NPs for use in high-performance gas sensors.

Clinical and Pathological Variation of Charcot-Marie-Tooth 1A in a Large Chinese Cohort.

Charcot-Marie-Tooth 1A (CMT1A) caused by peripheral myelin protein 22 (PMP22) gene duplication is the most common form of hereditary polyneuropathy. Twenty-four genetically confirmed CMT1A patients with sural nerve biopsies were enrolled in this study. The clinical picture included a great variability of phenotype with mean onset age of 22.2 ± 14.5 years (1-55 years). Pathologically, we observed a severe reduction in myelinated fiber density showing three types of changes: pure onion bulb formation in 3 cases (12.5%), onion bulb formation with axonal sprouts in 10 cases (41.7%), and focally thickened myelin with onion bulb formation or/and axonal sprouts in 11 cases (45.8%). We observed no significant correlation between nerve fiber density and disease duration. There was no significant difference between the 3 pathological types in terms of clinical manifestations, nerve fiber density, and g-ratio. Our study indicates that there is marked variability in the age of onset of CMT1A, as well as significant pathological changes without deterioration with the development of the disease. Focally thickened myelin is another common morphological feature of demyelination.

Similar clinical, pathological, and genetic features in Chinese patients with autosomal recessive and dominant Charcot-Marie-Tooth disease type 2K.

Mutations in the ganglioside-induced differentiation-associated protein 1 gene (GDAP1) cause rare subtypes of Charcot-Marie-Tooth disease (CMT2K and CMT4A). CMT2K is an axonal neuropathy while CMT4A is a demyelinating type. In a series of 169 Chinese CMT patients (79 CMT1, 52 CMT2 and 38 unclassified), four unrelated patients (2.37%) were identified with GDAP1 mutations, including two with autosomal recessive CMT2K (AR-CMT2K) and two dominant CMT2K (AD-CMT2K). All patients had disease onset before 5 years of age, and presented with muscle weakness, atrophy, and mild sensory disturbance in distal limbs. Motor nerve conduction velocities of the median nerve were within normal ranges, and compound muscle action potential ranged from 1.5 to 3.8 mV. Sural nerve biopsy revealed loss of large myelinated fibers with regeneration clusters and a few onion bulbs. Electron microscopy showed mitochondrial aggregation in both axons and Schwann cells, and neurofilament accumulation in giant unmyelinated fibers. The p.H256R mutation was found in all patients with GDAP1 compound heterozygous mutations, suggesting that it might be a common mutation in Chinese patients. This study observed no difference in the disease onset, phenotype severity, electrophysiological findings, or pathological changes between AR-CMT2K and AD-CMT2K patients.

A cohort study of Han Chinese MFN2-related Charcot-Marie-Tooth 2A.

BACKGROUND: Charcot-Marie-Tooth 2A (CMT2A) is caused by mutations in mitochondrial fusion protein mitofusin 2 (MFN2). CMT2A had a large variety of clinical symptoms and several cohort studies were published recently. This study is to summarized the clinical, electrophysiological, pathological and genetic features in Han Chinese CMT2A. METHODS: 20 patients from 12 unrelated Chinese families with MFN2 related CMT2A were collected. Clinical symptom, nerve conduction velocity study, sural nerve pathology and MFN2 gene mutation were retrospectively analyzed. RESULTS: We confirmed MFN2 gene mutation in 12 indexes. Nineteen of 20 (95%) patients were classified as early onset phenotypes of CMT2A, including four cases (20%) with infantile onset. Motor nerve conduction velocity (MNCV) of median nerve was above 38m/s in 50% of patients and not recordable in remaining patients. MNCV was not affected by onset age, disease course and mutation site in different patients and MNCV had no correlation with severity of symptoms. Sural nerve biopsy revealed mixed axonal and demyelination change. Loss of myelinated fibers and atypical onions was found in all cases. Electron microscopic (EM) examination of sural nerve confirmed mitochondrial vacuation and aggregation both in myelinated and unmyelinated axons. Eight mutations were detected in 12 indexes, including two novel mutations. The amino acid residue at position 94 of MFN2 protein was a hot spot in Han Chinese patients, followed by R104W. CONCLUSIONS: Eraly onset, even infantile onset was more common in our Chinese population. MNCV of median nerve could be either above 38m/s or unrecordable in CMT2A. Pathologically, mixed axon and myelin change should be considered since onion change was frequently observed in most CMT2A.