Charcot-Marie-Tooth Disease Type 2

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Inheritance

2

Autosomal Dominant

Most CMT2 subtypes follow autosomal dominant inheritance, including CMT2A (MFN2), CMT2B (RAB7A), CMT2D (GARS1), CMT2E (NEFL), and CMT2I/J (MPZ). De novo mutations occur, particularly in MFN2.

Show evidence (1 reference)

PMID:21327736 SUPPORT Other

"The majority of CMT2 are autosomal-dominant but autosomal-recessive forms have been described."

Review supports autosomal dominant inheritance as the most common CMT2 inheritance pattern.

Autosomal Recessive

Some CMT2 subtypes follow autosomal recessive inheritance, including CMT2B1 (LMNA), CMT2B2 (MED25), and SORD-CMT2. Recessive NEFL mutations also cause a severe early-onset form.

Show evidence (1 reference)

PMID:21327736 SUPPORT Other

"The majority of CMT2 are autosomal-dominant but autosomal-recessive forms have been described."

Review supports the presence of autosomal recessive CMT2 forms.

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Subtypes

6

CMT2A (MFN2-related)

The most common CMT2 subtype, caused by mutations in the MFN2 gene encoding mitofusin-2. Characterized by early onset, severe distal weakness, and optic atrophy in some cases.

Show evidence (1 reference)

PMID:32733278 SUPPORT Other

"A causal relationship between Mitofusin (MFN) 2 gene mutations and the hereditary axonal neuropathy Charcot-Marie-Tooth disease type 2A (CMT2A) was described over 15 years ago."

Establishes MFN2 mutations as the causal lesion for CMT2A.

CMT2E (NEFL-related)

Caused by mutations in NEFL encoding neurofilament light chain. Presents with variable severity, from mild to severe neuropathy.

Show evidence (1 reference)

PMID:34485306 SUPPORT In Vitro

"Here, we demonstrate that allele-specific CRISPR gene editing in a human model of axonal Charcot-Marie-Tooth (CMT) disease rescues pathology caused by a dominant missense mutation in the neurofilament light chain gene (NEFL, CMT type 2E)."

Confirms NEFL mutations as the molecular driver of CMT2E.

CMT2B (RAB7A-related)

Caused by mutations in RAB7A. Distinguished by prominent sensory loss with ulcerations and occasional amputations.

Show evidence (1 reference)

PMID:24521780 SUPPORT Model Organism

"Missense mutations in RAB7A, the gene encoding the small GTPase Rab7, cause CMT2B and increase Rab7 activity."

Establishes RAB7A mutations as the causal lesion for CMT2B.

CMT2D (GARS1-related)

Caused by mutations in GARS1 encoding glycyl-tRNA synthetase. Predominantly affects the upper extremities.

Show evidence (1 reference)

PMID:36928301 SUPPORT Model Organism

"Gain-of-function mutations in the housekeeping gene GARS1, which lead to the expression of toxic versions of glycyl-tRNA synthetase (GlyRS), cause the selective motor and sensory pathology characterizing Charcot-Marie-Tooth disease (CMT)."

Links pathogenic GARS1/GlyRS gain-of-function mutations to the motor and sensory pathology modeled in CMT2D.

CMT2I/J (MPZ-related)

Caused by mutations in MPZ encoding myelin protein zero. Late-onset axonal neuropathy with pupillary abnormalities.

Show evidence (1 reference)

PMID:27774063 SUPPORT Human Clinical

"Mutations in MPZ have been associated with different Charcot-Marie-Tooth disease (CMT) phenotypes (CMT1B, CMT2I/J, CMTDI), Dejerine-Sottas syndrome, and congenital hypomyelination neuropathy."

Establishes MPZ mutations as associated with the CMT2I/J phenotype spectrum.

SORD-related axonal CMT2

Autosomal recessive axonal neuropathy caused by biallelic loss-of-function SORD variants. SORD-CMT2 is associated with sorbitol dehydrogenase loss, elevated sorbitol, and distal motor-predominant axonal degeneration.

Show evidence (1 reference)

PMID:32367058 SUPPORT Human Clinical

"Here we report biallelic mutations in the sorbitol dehydrogenase gene (SORD) as the most frequent recessive form of hereditary neuropathy."

Establishes biallelic SORD variants as a common cause of autosomal recessive hereditary neuropathy in the CMT2 spectrum.

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Pathophysiology

7

Mitochondrial Fragmentation

MFN2 mutations impair mitochondrial outer membrane fusion, leading to fragmented mitochondria. Loss of fusion capacity prevents complementation of damaged mitochondrial DNA and proteins, resulting in dysfunctional mitochondrial networks in neurons.

Motor neuron link Sensory neuron link

MFN2 link

Mitochondrial fusion link ↓ DECREASED

Downstream

Impaired Mitochondrial Axonal Transport Fragmented mitochondria cannot be efficiently transported along axons, as mitofusin-2 also plays a direct role in mitochondrial motility and attachment to motor proteins.

Show evidence (2 references)

PMID:32733278 SUPPORT Other

"A causal relationship between Mitofusin (MFN) 2 gene mutations and the hereditary axonal neuropathy Charcot-Marie-Tooth disease type 2A (CMT2A) was described over 15 years ago."

Review establishes MFN2 as the causal gene for CMT2A and its role in mitochondrial fusion.

PMID:34602978 SUPPORT In Vitro

"MFN2 loss did not affect spinal motor neuron differentiation from hESCs but resulted in mitochondrial fragmentation and dysfunction as determined by live-cell imaging."

In vitro evidence that MFN2 deficiency causes mitochondrial fragmentation in human motor neurons.

Impaired Mitochondrial Axonal Transport

Fragmented mitochondria resulting from MFN2 dysfunction fail to be efficiently transported to distal axon terminals. MFN2 also directly regulates mitochondrial transport by interacting with the Miro/Milton motor adaptor complex. Energy deficits at distal terminals result from inadequate mitochondrial delivery.

Motor neuron link Sensory neuron link

MFN2 link

Axonal transport of mitochondria link ↓ DECREASED

Downstream

Distal Axonal Degeneration Failure of mitochondrial delivery to distal axon terminals causes energy failure and triggers length-dependent axonal degeneration.

Show evidence (1 reference)

PMID:34602978 SUPPORT In Vitro

"MFN2 deficit impaired anterograde and retrograde mitochondrial transport within axons, and reduced the mRNA and protein levels of kinesin and dynein, indicating the interfered motor protein expression induced by MFN2 deficiency."

Direct demonstration that MFN2 loss impairs bidirectional mitochondrial transport in human motor neuron axons.

Neurofilament Assembly Disruption

NEFL mutations cause abnormal neurofilament assembly and accumulation of neurofilament aggregates in neuronal cell bodies and proximal axons. Disrupted neurofilament stoichiometry impairs axonal caliber maintenance and reduces neurofilament density in myelinated axons, particularly affecting large-caliber fibers.

Motor neuron link

NEFL link

Neurofilament cytoskeleton organization link ⚠ ABNORMAL

Downstream

Distal Axonal Degeneration Disrupted neurofilament network impairs axonal caliber and slow axonal transport, contributing to axonal degeneration.

Show evidence (3 references)

PMID:12432080 SUPPORT In Vitro

"Both mutations disrupted the self-assembly of human NFL."

Direct demonstration that CMT2E NEFL mutations (P8R and Q333P) disrupt neurofilament assembly in cultured cells.

PMID:34485306 SUPPORT In Vitro

"Diseased motor neurons recapitulated known pathologic phenotypes at early time points of differentiation, including aberrant accumulation of neurofilament light chain protein in neuronal cell bodies."

iPSC-derived motor neurons from CMT2E patient with NEFL N98S mutation show neurofilament accumulation, directly linking NEFL mutations to neurofilament assembly disruption.

PMID:29940160 SUPPORT Model Organism

"the p.N98S mutation causes a profound reduction of neurofilaments in the myelinated axons of the PNS and CNS, resulting in substantially reduced axonal diameters, particularly of large myelinated axons, and distal axon loss in the PNS."

Mouse model of CMT2E with heterozygous Nefl N98S mutation confirms neurofilament reduction in axons and distal axon loss.

Impaired Endosomal Trafficking

RAB7A mutations impair late endosomal trafficking and lysosomal degradation in neurons. Defective endosome-to-lysosome maturation disrupts neurotrophin receptor signaling and cellular waste removal in long axons, particularly sensory neurons.

Sensory neuron link

RAB7A link

Endosome to lysosome transport link ⚠ ABNORMAL

Downstream

Distal Axonal Degeneration Defective endosomal trafficking impairs neurotrophin receptor signaling and autophagy, leading to sensory axon degeneration.

Show evidence (2 references)

PMID:34486665 SUPPORT In Vitro

"In Charcot-Marie-Tooth disease 2B (CMT2B), a neuropathy of the peripheral nervous system, this tubulating mechanism is disrupted."

Demonstrates that CMT2B RAB7A mutations disrupt endosomal tubulation and TrkA neurotrophin receptor retrieval.

PMID:24521780 SUPPORT Model Organism

"Missense mutations in RAB7A, the gene encoding the small GTPase Rab7, cause CMT2B and increase Rab7 activity. Rab7 is ubiquitously expressed and is involved in degradation through the lysosomal pathway."

Drosophila model confirms RAB7A mutations cause CMT2B through altered endosomal/lysosomal trafficking with sensory and motor phenotypes.

Impaired Neurotrophin Signaling Endosome Axonal Transport

GARS1 gain-of-function mutations produce toxic glycyl-tRNA synthetase variants that aberrantly interact with neurotrophin receptor pathways such as BDNF/TrkB. In CMT2D models, this disrupts axonal transport of neurotrophin-containing signaling endosomes, compromising trophic signaling in long peripheral axons.

Motor neuron link Sensory neuron link

GARS1 link

Axonal transport link ↓ DECREASED

Downstream

Distal Axonal Degeneration Persistent disruption of neurotrophin signaling endosome transport deprives long axons of trophic support and contributes to distal axonal degeneration.

Show evidence (2 references)

PMID:36928301 SUPPORT Model Organism

"Through intravital imaging of the sciatic nerve, we show that CMT2D mice displayed early and persistent disturbances in axonal transport of neurotrophin-containing signaling endosomes in vivo."

Directly supports impaired neurotrophin signaling endosome axonal transport in CMT2D mice.

PMID:36928301 SUPPORT Model Organism

"(BDNF)/TrkB impairments correlated with transport disruption and overall CMT2D neuropathology and that inhibition of this pathway at the nerve-muscle interface perturbed endosome transport in wild-type axons."

Links BDNF/TrkB pathway impairment to transport disruption and CMT2D neuropathology.

SORD Deficiency and Sorbitol Accumulation

Biallelic SORD loss-of-function variants reduce sorbitol dehydrogenase activity in the polyol pathway. Loss of SORD protein causes intracellular and serum sorbitol accumulation, which is linked to peripheral axon degeneration in patient cells and Drosophila models.

Motor neuron link Sensory neuron link

SORD link

Carbohydrate metabolic process link ⚠ ABNORMAL

Downstream

Distal Axonal Degeneration Sorbitol accumulation and polyol-pathway dysfunction contribute to the length-dependent peripheral axon degeneration seen in SORD-CMT2.

Show evidence (2 references)

PMID:32367058 SUPPORT In Vitro

"In patient-derived fibroblasts, we found a complete loss of SORD protein and increased intracellular sorbitol."

Patient-derived fibroblast evidence supports SORD protein loss and intracellular sorbitol accumulation.

PMID:32367058 SUPPORT Model Organism

"In Drosophila, loss of SORD orthologs caused synaptic degeneration and progressive motor impairment."

Model-organism evidence links SORD deficiency to synaptic degeneration and progressive motor impairment.

Distal Axonal Degeneration

The final common pathway in CMT2 involves dying-back degeneration of peripheral nerve axons. The longest axons are affected first due to their higher metabolic and transport demands, producing the characteristic length-dependent pattern of weakness and sensory loss. This is a Wallerian-like process distinct from neuronal apoptosis.

Motor neuron link Sensory neuron link

Autophagy link ↕ DYSREGULATED

Show evidence (2 references)

PMID:34606075 SUPPORT Other

"Genetic neuropathies that primarily cause axonal degeneration, as opposed to demyelination, are most often classified as Charcot-Marie-Tooth disease type 2 (CMT2) and are the focus of this review."

Authoritative review establishing CMT2 as defined by axonal degeneration rather than demyelination.

PMID:32733278 SUPPORT Other

"the challenge of defining the central underlying mechanism(s) linking mitochondrial abnormalities to progressive dying-back of peripheral arm and leg nerves in CMT2A is largely unmet"

Confirms the dying-back pattern of axonal degeneration as the hallmark of CMT2A pathology.

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Pathograph

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Phenotypes

7

Limbs 1

Foot Deformity (Pes Cavus) VERY_FREQUENT Pes cavus (HP:0001761)

Show evidence (1 reference)

PMID:40636623 SUPPORT Other

"As the disease progresses, individuals often develop foot drop and foot deformities such as pes cavus and equinus, leading to a significant decline in gait function."

Review confirms pes cavus as a hallmark foot deformity in CMT.

Musculoskeletal 1

Distal Muscle Weakness OBLIGATE Distal muscle weakness (HP:0002460)

Show evidence (1 reference)

PMID:34606075 SUPPORT Other

"Inherited peripheral neuropathies are a genetically and phenotypically diverse group of disorders that lead to degeneration of peripheral neurons with resulting sensory and motor dysfunction."

Review confirms motor dysfunction as a core feature of inherited axonal neuropathies including CMT2.

Nervous System 1

Reduced Deep Tendon Reflexes VERY_FREQUENT Areflexia (HP:0001284)

Other 4

Distal Sensory Loss VERY_FREQUENT Distal sensory impairment (HP:0002936)

Show evidence (1 reference)

PMID:24521780 SUPPORT Human Clinical

"It is characterised by prominent sensory loss, often complicated by severe ulcero-mutilations of toes or feet, and variable motor involvement."

Clinical characterization of CMT2B from the introduction of the paper, describing the human phenotype.

Distal Lower Limb Muscle Atrophy VERY_FREQUENT Distal lower limb amyotrophy (HP:0008944)

Show evidence (1 reference)

PMID:36445400 SUPPORT Other

"Hereditary motor neuropathies (HMN) were first defined as a group of neuromuscular disorders characterized by lower motor neuron dysfunction, slowly progressive length-dependent distal muscle weakness and atrophy, without sensory involvement."

Confirms distal muscle atrophy as a defining feature of hereditary motor neuropathies overlapping with CMT2.

Steppage Gait FREQUENT Steppage gait (HP:0003376)

Show evidence (1 reference)

PMID:40636623 SUPPORT Other

"One of the hallmark manifestations of CMT is gait disturbance. As the disease progresses, individuals often develop foot drop and foot deformities such as pes cavus and equinus, leading to a significant decline in gait function."

Review confirms gait disturbance including foot drop as a hallmark of CMT.

Distal Upper Limb Muscle Weakness FREQUENT Upper limb muscle weakness (HP:0003484)

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Genetic Associations

6

MFN2 (Causative)

Show evidence (1 reference)

PMID:32733278 SUPPORT Other

"A causal relationship between Mitofusin (MFN) 2 gene mutations and the hereditary axonal neuropathy Charcot-Marie-Tooth disease type 2A (CMT2A) was described over 15 years ago."

Establishes MFN2 as the causal gene for CMT2A.

NEFL (Causative)

Show evidence (2 references)

PMID:34485306 SUPPORT In Vitro

"Here, we demonstrate that allele-specific CRISPR gene editing in a human model of axonal Charcot-Marie-Tooth (CMT) disease rescues pathology caused by a dominant missense mutation in the neurofilament light chain gene (NEFL, CMT type 2E)."

Patient-derived motor neuron evidence confirms a dominant NEFL missense mutation as causal for CMT2E pathology.

CGGV:assertion_49d4cf82-b365-456e-9e35-2b28a66b71ec-2023-01-10T170000.000Z SUPPORT Other

ClinGen classifies the NEFL-Charcot-Marie-Tooth disease type 2 gene-disease relationship as definitive with autosomal recessive inheritance.

RAB7A (Causative)

Show evidence (2 references)

PMID:24521780 SUPPORT Model Organism

"Missense mutations in RAB7A, the gene encoding the small GTPase Rab7, cause CMT2B and increase Rab7 activity."

Confirms RAB7A mutations are causal for CMT2B.

CGGV:assertion_222dbfa6-db75-42a0-bab6-338b46a316c3-2022-02-10T021034.172Z SUPPORT Other

ClinGen classifies the RAB7A-Charcot-Marie-Tooth disease type 2 gene-disease relationship as definitive with autosomal dominant inheritance.

GARS1 (Causative)

Show evidence (1 reference)

PMID:36928301 SUPPORT Model Organism

"Aberrant interactions between GlyRS mutants and different proteins, including neurotrophin receptor tropomyosin receptor kinase receptor B (TrkB), underlie CMT type 2D (CMT2D); however, our pathomechanistic understanding of this untreatable peripheral neuropathy remains incomplete."

Supports GARS1/GlyRS mutant pathology as the causal basis of CMT2D.

MPZ (Causative)

Show evidence (1 reference)

PMID:27774063 SUPPORT Human Clinical

"The MPZ mutation Asp121Asn may be associated with late-onset axonal neuropathy, early onset hearing loss and pupil abnormalities."

Human family evidence supports MPZ mutation association with late-onset axonal CMT2I/J features.

SORD (Causative)

Show evidence (1 reference)

PMID:32367058 SUPPORT Human Clinical

"Here we report biallelic mutations in the sorbitol dehydrogenase gene (SORD) as the most frequent recessive form of hereditary neuropathy."

Establishes biallelic SORD variants as causative for an autosomal recessive hereditary neuropathy in the CMT2 spectrum.

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Treatments

7

Physical Therapy and Rehabilitation

Action: physical therapy Ontology label: Physical Therapy NCIT:C15302

Regular physical therapy to maintain muscle strength, flexibility, and range of motion. Includes stretching exercises, strengthening of unaffected muscles, and balance training.

Show evidence (1 reference)

PMID:40636623 SUPPORT Other

"While physical therapy may improve muscle strength and physical function, the quality of evidence remains moderate, and no standardized rehabilitation protocols have been firmly established."

Review supports physical therapy for CMT while noting evidence quality is moderate.

Orthotic Devices

Action: orthotic supportive care Ontology label: Supportive Care NCIT:C15747

Ankle-foot orthoses (AFOs) to compensate for foot drop and improve gait stability. Custom orthopedic shoes for foot deformities.

Show evidence (1 reference)

PMID:40636623 SUPPORT Other

"Management focuses on symptomatic interventions, including orthotic support, surgical procedures, and physical therapy."

Review confirms orthotic support as a standard management strategy for CMT.

Surgical Management

Action: orthopedic surgical procedure Ontology label: Orthopedic Surgical Procedure NCIT:C16186

Corrective surgery for severe foot deformities including tendon transfers, osteotomies, and arthrodesis. Considered when conservative measures fail to maintain functional ambulation.

Avoidance of Neurotoxic Medications

Action: supportive care Ontology label: Supportive Care NCIT:C15747

Patients should avoid medications known to worsen peripheral neuropathy, particularly vincristine, which can cause severe deterioration in CMT patients.

Genetic Counseling

Action: genetic counseling MAXO:0000079

Genetic counseling supports inheritance-risk assessment, cascade testing, reproductive counseling, and interpretation of molecular diagnoses for families affected by genetically heterogeneous CMT2.

Show evidence (1 reference)

PMID:20301532 SUPPORT Other

"Inform genetic counseling of family members of an individual with CMT hereditary neuropathy."

GeneReviews explicitly includes genetic counseling for family members as part of CMT hereditary neuropathy management.

Epalrestat for SORD-CMT2

Action: Pharmacotherapy NCIT:C15986

Agent: epalrestat ↗

Epalrestat is an aldose reductase inhibitor under Phase II evaluation for SORD-CMT2. It targets the upstream polyol pathway to reduce sorbitol production in patients with SORD deficiency; clinical efficacy remains investigational.

Mechanism Target:

SORD Deficiency and Sorbitol Accumulation — Epalrestat inhibits aldose reductase upstream of SORD, aiming to reduce sorbitol accumulation caused by SORD deficiency.

Target Phenotypes: Distal muscle weakness ↗

Show evidence (2 references)

clinicaltrials:NCT05777226 PARTIAL Human Clinical

"The primary purpose of this study is to explore the natural history of SORD-CMT2 patients by detecting the ONLS scale score and serum sorbitol level changes at 6th, 12th, 24th, and 36th months and to evaluate the effectiveness and safety of epalrestat."

ClinicalTrials.gov documents a SORD-CMT2 epalrestat study, but results are not yet available.

PMID:32367058 SUPPORT In Vitro

"normalized intracellular sorbitol levels in patient-derived fibroblasts"

Patient-derived fibroblast evidence supports aldose reductase inhibition as a substrate-reduction strategy for SORD deficiency.

NMD670 for CMT1/CMT2

Action: Pharmacotherapy NCIT:C15986

NMD670 is an investigational small-molecule therapy tested in a completed Phase IIa placebo-controlled trial enrolling ambulatory adults with CMT1 or CMT2. The treatment is modeled with partial support because the trial record establishes clinical evaluation in CMT2 but does not provide outcome results in the cache.

Target Phenotypes: Steppage gait ↗ Distal muscle weakness ↗

Show evidence (1 reference)

clinicaltrials:NCT06482437 PARTIAL Human Clinical

"This Phase 2a study aims to evaluate the efficacy, safety and tolerability of NMD670 vs placebo administered twice a day (BID) for 21 days in ambulatory adult patients with Charcot-Marie-Tooth disease type 1 and type 2."

ClinicalTrials.gov documents completed Phase IIa clinical evaluation of NMD670 in adults with CMT1 or CMT2, but the cache does not include efficacy results.

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Clinical Trials

2

NCT05777226 PHASE_II NOT_RECRUITING

Multicenter Phase II study of SORD-CMT2 natural history and epalrestat treatment, measuring ONLS and serum sorbitol over 36 months in about 30 participants with SORD-CMT2.

Target Phenotypes: Distal muscle weakness ↗

Show evidence (1 reference)

clinicaltrials:NCT05777226 SUPPORT Human Clinical

"Patients in the drug treatment group take epalrestat (50 mg) orally three times daily."

Trial registry evidence documents epalrestat dosing in SORD-CMT2.

NCT06482437 PHASE_II COMPLETED

Phase IIa randomized, double-blind, placebo-controlled trial of NMD670 over 21 days in ambulatory adults with genetically confirmed Charcot-Marie-Tooth disease type 1 or type 2.

Target Phenotypes: Steppage gait ↗ Distal muscle weakness ↗

Show evidence (1 reference)

clinicaltrials:NCT06482437 SUPPORT Human Clinical

"This Phase 2a study aims to evaluate the efficacy, safety and tolerability of NMD670 vs placebo administered twice a day (BID) for 21 days in ambulatory adult patients with Charcot-Marie-Tooth disease type 1 and type 2."

Trial registry evidence documents a completed Phase IIa NMD670 trial that included CMT2.

{ }

Source YAML

click to show

name: Charcot-Marie-Tooth Disease Type 2
creation_date: "2026-04-08T23:00:00Z"
updated_date: "2026-04-29T01:06:55Z"
category: Genetic
description: >
  Charcot-Marie-Tooth disease type 2 (CMT2) is a group of inherited peripheral
  neuropathies characterized by axonal degeneration of peripheral nerves without
  primary demyelination. Unlike CMT1, which involves Schwann cell dysfunction and
  demyelination, CMT2 is primarily an axonopathy with normal or near-normal nerve
  conduction velocities (>38 m/s) but reduced compound muscle action potential
  amplitudes. CMT2 is genetically heterogeneous, with over 20 subtypes identified,
  the most common being CMT2A (MFN2 mutations) and CMT2E (NEFL mutations).
  Clinical features include progressive distal muscle weakness and atrophy,
  sensory loss, foot deformities, and areflexia, typically with onset in the
  first to second decade of life.
disease_term:
  preferred_term: Charcot-Marie-Tooth disease type 2
  term:
    id: MONDO:0018993
    label: Charcot-Marie-Tooth disease type 2
parents:
- Charcot-Marie-Tooth disease
has_subtypes:
- name: CMT2A
  display_name: CMT2A (MFN2-related)
  description: >
    The most common CMT2 subtype, caused by mutations in the MFN2 gene encoding
    mitofusin-2. Characterized by early onset, severe distal weakness, and optic
    atrophy in some cases.
  evidence:
  - reference: PMID:32733278
    reference_title: "Mitofusin 2 Dysfunction and Disease in Mice and Men."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "A causal relationship between Mitofusin (MFN) 2 gene mutations and the hereditary axonal neuropathy Charcot-Marie-Tooth disease type 2A (CMT2A) was described over 15 years ago."
    explanation: Establishes MFN2 mutations as the causal lesion for CMT2A.
- name: CMT2E
  display_name: CMT2E (NEFL-related)
  description: >
    Caused by mutations in NEFL encoding neurofilament light chain. Presents
    with variable severity, from mild to severe neuropathy.
  evidence:
  - reference: PMID:34485306
    reference_title: "Allele-Specific Gene Editing Rescues Pathology in a Human Model of Charcot-Marie-Tooth Disease Type 2E."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here, we demonstrate that allele-specific CRISPR gene editing in a human model of axonal Charcot-Marie-Tooth (CMT) disease rescues pathology caused by a dominant missense mutation in the neurofilament light chain gene (NEFL, CMT type 2E)."
    explanation: Confirms NEFL mutations as the molecular driver of CMT2E.
- name: CMT2B
  display_name: CMT2B (RAB7A-related)
  description: >
    Caused by mutations in RAB7A. Distinguished by prominent sensory loss
    with ulcerations and occasional amputations.
  evidence:
  - reference: PMID:24521780
    reference_title: "Human Rab7 mutation mimics features of Charcot-Marie-Tooth neuropathy type 2B in Drosophila."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Missense mutations in RAB7A, the gene encoding the small GTPase Rab7, cause CMT2B and increase Rab7 activity."
    explanation: Establishes RAB7A mutations as the causal lesion for CMT2B.
- name: CMT2D
  display_name: CMT2D (GARS1-related)
  description: >
    Caused by mutations in GARS1 encoding glycyl-tRNA synthetase. Predominantly
    affects the upper extremities.
  evidence:
  - reference: PMID:36928301
    reference_title: "Boosting peripheral BDNF rescues impaired in vivo axonal transport in CMT2D mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Gain-of-function mutations in the housekeeping gene GARS1, which lead to the expression of toxic versions of glycyl-tRNA synthetase (GlyRS), cause the selective motor and sensory pathology characterizing Charcot-Marie-Tooth disease (CMT)."
    explanation: Links pathogenic GARS1/GlyRS gain-of-function mutations to the motor and sensory pathology modeled in CMT2D.
- name: CMT2I/J
  display_name: CMT2I/J (MPZ-related)
  description: >
    Caused by mutations in MPZ encoding myelin protein zero. Late-onset axonal
    neuropathy with pupillary abnormalities.
  evidence:
  - reference: PMID:27774063
    reference_title: "A Novel Asp121Asn Mutation of Myelin Protein Zero Is Associated with Late-Onset Axonal Charcot-Marie-Tooth Disease, Hearing Loss and Pupil Abnormalities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in MPZ have been associated with different Charcot-Marie-Tooth disease (CMT) phenotypes (CMT1B, CMT2I/J, CMTDI), Dejerine-Sottas syndrome, and congenital hypomyelination neuropathy."
    explanation: Establishes MPZ mutations as associated with the CMT2I/J phenotype spectrum.
- name: SORD-CMT2
  display_name: SORD-related axonal CMT2
  description: >
    Autosomal recessive axonal neuropathy caused by biallelic loss-of-function
    SORD variants. SORD-CMT2 is associated with sorbitol dehydrogenase loss,
    elevated sorbitol, and distal motor-predominant axonal degeneration.
  evidence:
  - reference: PMID:32367058
    reference_title: "Biallelic mutations in SORD cause a common and potentially treatable hereditary neuropathy with implications for diabetes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we report biallelic mutations in the sorbitol dehydrogenase gene (SORD) as the most frequent recessive form of hereditary neuropathy."
    explanation: Establishes biallelic SORD variants as a common cause of autosomal recessive hereditary neuropathy in the CMT2 spectrum.
pathophysiology:
- name: Mitochondrial Fragmentation
  description: >
    MFN2 mutations impair mitochondrial outer membrane fusion, leading to
    fragmented mitochondria. Loss of fusion capacity prevents complementation
    of damaged mitochondrial DNA and proteins, resulting in dysfunctional
    mitochondrial networks in neurons.
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  biological_processes:
  - preferred_term: Mitochondrial fusion
    term:
      id: GO:0008053
      label: mitochondrial fusion
    modifier: DECREASED
  genes:
  - preferred_term: MFN2
    term:
      id: hgnc:16877
      label: MFN2
  downstream:
  - target: Impaired Mitochondrial Axonal Transport
    description: >
      Fragmented mitochondria cannot be efficiently transported along
      axons, as mitofusin-2 also plays a direct role in mitochondrial
      motility and attachment to motor proteins.
  evidence:
  - reference: PMID:32733278
    reference_title: "Mitofusin 2 Dysfunction and Disease in Mice and Men."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "A causal relationship between Mitofusin (MFN) 2 gene mutations and the hereditary axonal neuropathy Charcot-Marie-Tooth disease type 2A (CMT2A) was described over 15 years ago."
    explanation: Review establishes MFN2 as the causal gene for CMT2A and its role in mitochondrial fusion.
  - reference: PMID:34602978
    reference_title: "MFN2 Deficiency Impairs Mitochondrial Transport and Downregulates Motor Protein Expression in Human Spinal Motor Neurons."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "MFN2 loss did not affect spinal motor neuron differentiation from hESCs but resulted in mitochondrial fragmentation and dysfunction as determined by live-cell imaging."
    explanation: In vitro evidence that MFN2 deficiency causes mitochondrial fragmentation in human motor neurons.
  notes: Subtype CMT2A (MFN2 mutations) is the most common CMT2 subtype

- name: Impaired Mitochondrial Axonal Transport
  description: >
    Fragmented mitochondria resulting from MFN2 dysfunction fail to be
    efficiently transported to distal axon terminals. MFN2 also directly
    regulates mitochondrial transport by interacting with the Miro/Milton
    motor adaptor complex. Energy deficits at distal terminals result from
    inadequate mitochondrial delivery.
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  biological_processes:
  - preferred_term: Axonal transport of mitochondria
    term:
      id: GO:0019896
      label: axonal transport of mitochondrion
    modifier: DECREASED
  genes:
  - preferred_term: MFN2
    term:
      id: hgnc:16877
      label: MFN2
  downstream:
  - target: Distal Axonal Degeneration
    description: >
      Failure of mitochondrial delivery to distal axon terminals causes
      energy failure and triggers length-dependent axonal degeneration.
  evidence:
  - reference: PMID:34602978
    reference_title: "MFN2 Deficiency Impairs Mitochondrial Transport and Downregulates Motor Protein Expression in Human Spinal Motor Neurons."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "MFN2 deficit impaired anterograde and retrograde mitochondrial transport within axons, and reduced the mRNA and protein levels of kinesin and dynein, indicating the interfered motor protein expression induced by MFN2 deficiency."
    explanation: Direct demonstration that MFN2 loss impairs bidirectional mitochondrial transport in human motor neuron axons.

- name: Neurofilament Assembly Disruption
  description: >
    NEFL mutations cause abnormal neurofilament assembly and accumulation
    of neurofilament aggregates in neuronal cell bodies and proximal axons.
    Disrupted neurofilament stoichiometry impairs axonal caliber maintenance
    and reduces neurofilament density in myelinated axons, particularly
    affecting large-caliber fibers.
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  biological_processes:
  - preferred_term: Neurofilament cytoskeleton organization
    term:
      id: GO:0060052
      label: neurofilament cytoskeleton organization
    modifier: ABNORMAL
  genes:
  - preferred_term: NEFL
    term:
      id: hgnc:7739
      label: NEFL
  downstream:
  - target: Distal Axonal Degeneration
    description: >
      Disrupted neurofilament network impairs axonal caliber and slow
      axonal transport, contributing to axonal degeneration.
  evidence:
  - reference: PMID:12432080
    reference_title: "Effects of Charcot-Marie-Tooth-linked mutations of the neurofilament light subunit on intermediate filament formation."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Both mutations disrupted the self-assembly of human NFL."
    explanation: Direct demonstration that CMT2E NEFL mutations (P8R and Q333P) disrupt neurofilament assembly in cultured cells.
  - reference: PMID:34485306
    reference_title: "Allele-Specific Gene Editing Rescues Pathology in a Human Model of Charcot-Marie-Tooth Disease Type 2E."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Diseased motor neurons recapitulated known pathologic phenotypes at early time points of differentiation, including aberrant accumulation of neurofilament light chain protein in neuronal cell bodies."
    explanation: iPSC-derived motor neurons from CMT2E patient with NEFL N98S mutation show neurofilament accumulation, directly linking NEFL mutations to neurofilament assembly disruption.
  - reference: PMID:29940160
    reference_title: "Myelinated axons fail to develop properly in a genetically authentic mouse model of Charcot-Marie-Tooth disease type 2E."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "the p.N98S mutation causes a profound reduction of neurofilaments in the myelinated axons of the PNS and CNS, resulting in substantially reduced axonal diameters, particularly of large myelinated axons, and distal axon loss in the PNS."
    explanation: Mouse model of CMT2E with heterozygous Nefl N98S mutation confirms neurofilament reduction in axons and distal axon loss.
  notes: Subtype CMT2E (NEFL mutations)

- name: Impaired Endosomal Trafficking
  description: >
    RAB7A mutations impair late endosomal trafficking and lysosomal
    degradation in neurons. Defective endosome-to-lysosome maturation
    disrupts neurotrophin receptor signaling and cellular waste removal
    in long axons, particularly sensory neurons.
  cell_types:
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  biological_processes:
  - preferred_term: Endosome to lysosome transport
    term:
      id: GO:0008333
      label: endosome to lysosome transport
    modifier: ABNORMAL
  genes:
  - preferred_term: RAB7A
    term:
      id: hgnc:9788
      label: RAB7A
  downstream:
  - target: Distal Axonal Degeneration
    description: >
      Defective endosomal trafficking impairs neurotrophin receptor
      signaling and autophagy, leading to sensory axon degeneration.
  evidence:
  - reference: PMID:34486665
    reference_title: "Tubular microdomains of Rab7-positive endosomes retrieve TrkA, a mechanism disrupted in Charcot-Marie-Tooth disease 2B."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In Charcot-Marie-Tooth disease 2B (CMT2B), a neuropathy of the peripheral nervous system, this tubulating mechanism is disrupted."
    explanation: Demonstrates that CMT2B RAB7A mutations disrupt endosomal tubulation and TrkA neurotrophin receptor retrieval.
  - reference: PMID:24521780
    reference_title: "Human Rab7 mutation mimics features of Charcot-Marie-Tooth neuropathy type 2B in Drosophila."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Missense mutations in RAB7A, the gene encoding the small GTPase Rab7, cause CMT2B and increase Rab7 activity. Rab7 is ubiquitously expressed and is involved in degradation through the lysosomal pathway."
    explanation: Drosophila model confirms RAB7A mutations cause CMT2B through altered endosomal/lysosomal trafficking with sensory and motor phenotypes.
  notes: Subtype CMT2B with prominent sensory involvement and ulcerations

- name: Impaired Neurotrophin Signaling Endosome Axonal Transport
  description: >
    GARS1 gain-of-function mutations produce toxic glycyl-tRNA synthetase
    variants that aberrantly interact with neurotrophin receptor pathways such
    as BDNF/TrkB. In CMT2D models, this disrupts axonal transport of
    neurotrophin-containing signaling endosomes, compromising trophic signaling
    in long peripheral axons.
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  biological_processes:
  - preferred_term: Axonal transport
    term:
      id: GO:0098930
      label: axonal transport
    modifier: DECREASED
  genes:
  - preferred_term: GARS1
    term:
      id: hgnc:4162
      label: GARS1
  downstream:
  - target: Distal Axonal Degeneration
    description: >
      Persistent disruption of neurotrophin signaling endosome transport
      deprives long axons of trophic support and contributes to distal axonal
      degeneration.
  evidence:
  - reference: PMID:36928301
    reference_title: "Boosting peripheral BDNF rescues impaired in vivo axonal transport in CMT2D mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Through intravital imaging of the sciatic nerve, we show that CMT2D mice displayed early and persistent disturbances in axonal transport of neurotrophin-containing signaling endosomes in vivo."
    explanation: Directly supports impaired neurotrophin signaling endosome axonal transport in CMT2D mice.
  - reference: PMID:36928301
    reference_title: "Boosting peripheral BDNF rescues impaired in vivo axonal transport in CMT2D mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "(BDNF)/TrkB impairments correlated with transport disruption and overall CMT2D neuropathology and that inhibition of this pathway at the nerve-muscle interface perturbed endosome transport in wild-type axons."
    explanation: Links BDNF/TrkB pathway impairment to transport disruption and CMT2D neuropathology.
  notes: Subtype CMT2D (GARS1 mutations)

- name: SORD Deficiency and Sorbitol Accumulation
  description: >
    Biallelic SORD loss-of-function variants reduce sorbitol dehydrogenase
    activity in the polyol pathway. Loss of SORD protein causes intracellular
    and serum sorbitol accumulation, which is linked to peripheral axon
    degeneration in patient cells and Drosophila models.
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  biological_processes:
  - preferred_term: Carbohydrate metabolic process
    term:
      id: GO:0005975
      label: carbohydrate metabolic process
    modifier: ABNORMAL
  genes:
  - preferred_term: SORD
    term:
      id: hgnc:11184
      label: SORD
  downstream:
  - target: Distal Axonal Degeneration
    description: >
      Sorbitol accumulation and polyol-pathway dysfunction contribute to the
      length-dependent peripheral axon degeneration seen in SORD-CMT2.
  evidence:
  - reference: PMID:32367058
    reference_title: "Biallelic mutations in SORD cause a common and potentially treatable hereditary neuropathy with implications for diabetes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In patient-derived fibroblasts, we found a complete loss of SORD protein and increased intracellular sorbitol."
    explanation: Patient-derived fibroblast evidence supports SORD protein loss and intracellular sorbitol accumulation.
  - reference: PMID:32367058
    reference_title: "Biallelic mutations in SORD cause a common and potentially treatable hereditary neuropathy with implications for diabetes."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In Drosophila, loss of SORD orthologs caused synaptic degeneration and progressive motor impairment."
    explanation: Model-organism evidence links SORD deficiency to synaptic degeneration and progressive motor impairment.
  notes: SORD-related axonal neuropathy / autosomal recessive CMT2

- name: Distal Axonal Degeneration
  description: >
    The final common pathway in CMT2 involves dying-back degeneration of
    peripheral nerve axons. The longest axons are affected first due to
    their higher metabolic and transport demands, producing the characteristic
    length-dependent pattern of weakness and sensory loss. This is a
    Wallerian-like process distinct from neuronal apoptosis.
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Sensory neuron
    term:
      id: CL:0000101
      label: sensory neuron
  biological_processes:
  - preferred_term: Autophagy
    term:
      id: GO:0006914
      label: autophagy
    modifier: DYSREGULATED
  evidence:
  - reference: PMID:34606075
    reference_title: "Axonal Charcot-Marie-Tooth Disease: from Common Pathogenic Mechanisms to Emerging Treatment Opportunities."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Genetic neuropathies that primarily cause axonal degeneration, as opposed to demyelination, are most often classified as Charcot-Marie-Tooth disease type 2 (CMT2) and are the focus of this review."
    explanation: Authoritative review establishing CMT2 as defined by axonal degeneration rather than demyelination.
  - reference: PMID:32733278
    reference_title: "Mitofusin 2 Dysfunction and Disease in Mice and Men."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "the challenge of defining the central underlying mechanism(s) linking mitochondrial abnormalities to progressive dying-back of peripheral arm and leg nerves in CMT2A is largely unmet"
    explanation: Confirms the dying-back pattern of axonal degeneration as the hallmark of CMT2A pathology.

phenotypes:
- name: Distal Muscle Weakness
  category: Musculoskeletal
  frequency: OBLIGATE
  description: >
    Progressive weakness of distal limb muscles, particularly affecting
    the peroneal muscles of the lower legs and intrinsic hand muscles.
    Leads to difficulty with foot dorsiflexion (foot drop) and fine
    motor tasks.
  phenotype_term:
    preferred_term: Distal muscle weakness
    term:
      id: HP:0002460
      label: Distal muscle weakness
  evidence:
  - reference: PMID:34606075
    reference_title: "Axonal Charcot-Marie-Tooth Disease: from Common Pathogenic Mechanisms to Emerging Treatment Opportunities."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Inherited peripheral neuropathies are a genetically and phenotypically diverse group of disorders that lead to degeneration of peripheral neurons with resulting sensory and motor dysfunction."
    explanation: Review confirms motor dysfunction as a core feature of inherited axonal neuropathies including CMT2.

- name: Distal Sensory Loss
  category: Neurological
  frequency: VERY_FREQUENT
  description: >
    Progressive sensory loss in a stocking-glove distribution, affecting
    vibration and proprioception more than pain and temperature in most
    subtypes.
  phenotype_term:
    preferred_term: Distal sensory impairment
    term:
      id: HP:0002936
      label: Distal sensory impairment
  evidence:
  - reference: PMID:24521780
    reference_title: "Human Rab7 mutation mimics features of Charcot-Marie-Tooth neuropathy type 2B in Drosophila."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is characterised by prominent sensory loss, often complicated by severe ulcero-mutilations of toes or feet, and variable motor involvement."
    explanation: Clinical characterization of CMT2B from the introduction of the paper, describing the human phenotype.

- name: Foot Deformity (Pes Cavus)
  category: Musculoskeletal
  frequency: VERY_FREQUENT
  description: >
    High-arched feet (pes cavus) resulting from imbalance between
    intrinsic and extrinsic foot muscles. Often accompanied by
    hammer toes and equinovarus deformity.
  phenotype_term:
    preferred_term: Pes cavus
    term:
      id: HP:0001761
      label: Pes cavus
  evidence:
  - reference: PMID:40636623
    reference_title: "Clinical Characteristics of Gait Disturbance in Charcot-Marie-Tooth Disease and Future Directions in Physical Therapy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "As the disease progresses, individuals often develop foot drop and foot deformities such as pes cavus and equinus, leading to a significant decline in gait function."
    explanation: Review confirms pes cavus as a hallmark foot deformity in CMT.

- name: Distal Lower Limb Muscle Atrophy
  category: Musculoskeletal
  frequency: VERY_FREQUENT
  description: >
    Wasting of distal leg muscles producing the characteristic inverted
    champagne bottle or stork leg appearance.
  phenotype_term:
    preferred_term: Distal lower limb amyotrophy
    term:
      id: HP:0008944
      label: Distal lower limb amyotrophy
  evidence:
  - reference: PMID:36445400
    reference_title: "Early onset hereditary neuronopathies: an update on non-5q motor neuron diseases."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Hereditary motor neuropathies (HMN) were first defined as a group of neuromuscular disorders characterized by lower motor neuron dysfunction, slowly progressive length-dependent distal muscle weakness and atrophy, without sensory involvement."
    explanation: Confirms distal muscle atrophy as a defining feature of hereditary motor neuropathies overlapping with CMT2.

- name: Reduced Deep Tendon Reflexes
  category: Neurological
  frequency: VERY_FREQUENT
  description: >
    Absent or reduced deep tendon reflexes, particularly at the ankles,
    reflecting loss of the afferent sensory arc.
  phenotype_term:
    preferred_term: Areflexia
    term:
      id: HP:0001284
      label: Areflexia

- name: Steppage Gait
  category: Neurological
  frequency: FREQUENT
  description: >
    Characteristic high-stepping gait due to foot drop from peroneal
    muscle weakness, requiring exaggerated hip and knee flexion during
    the swing phase of walking.
  phenotype_term:
    preferred_term: Steppage gait
    term:
      id: HP:0003376
      label: Steppage gait
  evidence:
  - reference: PMID:40636623
    reference_title: "Clinical Characteristics of Gait Disturbance in Charcot-Marie-Tooth Disease and Future Directions in Physical Therapy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "One of the hallmark manifestations of CMT is gait disturbance. As the disease progresses, individuals often develop foot drop and foot deformities such as pes cavus and equinus, leading to a significant decline in gait function."
    explanation: Review confirms gait disturbance including foot drop as a hallmark of CMT.

- name: Distal Upper Limb Muscle Weakness
  category: Musculoskeletal
  frequency: FREQUENT
  description: >
    Weakness of intrinsic hand muscles developing later in the disease
    course, affecting grip strength and fine motor skills.
  phenotype_term:
    preferred_term: Distal upper limb muscle weakness
    term:
      id: HP:0003484
      label: Upper limb muscle weakness

genetic:
- name: MFN2
  association: Causative
  features: Most common CMT2 gene, accounting for ~20% of CMT2 cases with severe early-onset phenotype and optic atrophy in some patients
  subtype: CMT2A
  evidence:
  - reference: PMID:32733278
    reference_title: "Mitofusin 2 Dysfunction and Disease in Mice and Men."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "A causal relationship between Mitofusin (MFN) 2 gene mutations and the hereditary axonal neuropathy Charcot-Marie-Tooth disease type 2A (CMT2A) was described over 15 years ago."
    explanation: Establishes MFN2 as the causal gene for CMT2A.

- name: NEFL
  association: Causative
  notes: Both dominant missense and recessive null mutations described causing CMT2E
  subtype: CMT2E
  evidence:
  - reference: PMID:34485306
    reference_title: "Allele-Specific Gene Editing Rescues Pathology in a Human Model of Charcot-Marie-Tooth Disease Type 2E."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here, we demonstrate that allele-specific CRISPR gene editing in a human model of axonal Charcot-Marie-Tooth (CMT) disease rescues pathology caused by a dominant missense mutation in the neurofilament light chain gene (NEFL, CMT type 2E)."
    explanation: Patient-derived motor neuron evidence confirms a dominant NEFL missense mutation as causal for CMT2E pathology.

  - reference: CGGV:assertion_49d4cf82-b365-456e-9e35-2b28a66b71ec-2023-01-10T170000.000Z
    reference_title: "NEFL / Charcot-Marie-Tooth disease type 2 (Definitive)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "NEFL | HGNC:7739 | Charcot-Marie-Tooth disease type 2 | MONDO:0018993 | AR | Definitive"
    explanation: ClinGen classifies the NEFL-Charcot-Marie-Tooth disease type 2 gene-disease relationship as definitive with autosomal recessive inheritance.
- name: RAB7A
  association: Causative
  notes: RAB7A regulates late endosomal and lysosomal trafficking; mutations cause CMT2B with prominent sensory involvement
  subtype: CMT2B
  evidence:
  - reference: PMID:24521780
    reference_title: "Human Rab7 mutation mimics features of Charcot-Marie-Tooth neuropathy type 2B in Drosophila."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Missense mutations in RAB7A, the gene encoding the small GTPase Rab7, cause CMT2B and increase Rab7 activity."
    explanation: Confirms RAB7A mutations are causal for CMT2B.

  - reference: CGGV:assertion_222dbfa6-db75-42a0-bab6-338b46a316c3-2022-02-10T021034.172Z
    reference_title: "RAB7A / Charcot-Marie-Tooth disease type 2 (Definitive)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "RAB7A | HGNC:9788 | Charcot-Marie-Tooth disease type 2 | MONDO:0018993 | AD | Definitive"
    explanation: ClinGen classifies the RAB7A-Charcot-Marie-Tooth disease type 2 gene-disease relationship as definitive with autosomal dominant inheritance.
- name: GARS1
  association: Causative
  notes: Encodes glycyl-tRNA synthetase; mutations cause CMT2D with predominantly upper extremity involvement
  subtype: CMT2D
  evidence:
  - reference: PMID:36928301
    reference_title: "Boosting peripheral BDNF rescues impaired in vivo axonal transport in CMT2D mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Aberrant interactions between GlyRS mutants and different proteins, including neurotrophin receptor tropomyosin receptor kinase receptor B (TrkB), underlie CMT type 2D (CMT2D); however, our pathomechanistic understanding of this untreatable peripheral neuropathy remains incomplete."
    explanation: Supports GARS1/GlyRS mutant pathology as the causal basis of CMT2D.

- name: MPZ
  association: Causative
  notes: Myelin protein zero mutations can cause late-onset axonal CMT2I/J with pupillary abnormalities
  subtype: CMT2I/J
  evidence:
  - reference: PMID:27774063
    reference_title: "A Novel Asp121Asn Mutation of Myelin Protein Zero Is Associated with Late-Onset Axonal Charcot-Marie-Tooth Disease, Hearing Loss and Pupil Abnormalities."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The MPZ mutation Asp121Asn may be associated with late-onset axonal neuropathy, early onset hearing loss and pupil abnormalities."
    explanation: Human family evidence supports MPZ mutation association with late-onset axonal CMT2I/J features.

- name: SORD
  association: Causative
  notes: Biallelic SORD loss-of-function variants cause autosomal recessive SORD-related axonal CMT2 / distal hereditary motor neuropathy.
  subtype: SORD-CMT2
  evidence:
  - reference: PMID:32367058
    reference_title: "Biallelic mutations in SORD cause a common and potentially treatable hereditary neuropathy with implications for diabetes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we report biallelic mutations in the sorbitol dehydrogenase gene (SORD) as the most frequent recessive form of hereditary neuropathy."
    explanation: Establishes biallelic SORD variants as causative for an autosomal recessive hereditary neuropathy in the CMT2 spectrum.

inheritance:
- name: Autosomal Dominant
  description: >
    Most CMT2 subtypes follow autosomal dominant inheritance, including
    CMT2A (MFN2), CMT2B (RAB7A), CMT2D (GARS1), CMT2E (NEFL), and
    CMT2I/J (MPZ). De novo mutations occur, particularly in MFN2.
  evidence:
  - reference: PMID:21327736
    reference_title: "Recent advances in the genetics of hereditary axonal sensory-motor neuropathies type 2."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The majority of CMT2 are autosomal-dominant but autosomal-recessive forms have been described."
    explanation: Review supports autosomal dominant inheritance as the most common CMT2 inheritance pattern.

- name: Autosomal Recessive
  description: >
    Some CMT2 subtypes follow autosomal recessive inheritance, including
    CMT2B1 (LMNA), CMT2B2 (MED25), and SORD-CMT2. Recessive NEFL mutations
    also cause a severe early-onset form.
  evidence:
  - reference: PMID:21327736
    reference_title: "Recent advances in the genetics of hereditary axonal sensory-motor neuropathies type 2."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The majority of CMT2 are autosomal-dominant but autosomal-recessive forms have been described."
    explanation: Review supports the presence of autosomal recessive CMT2 forms.

diagnosis:
- name: Nerve Conduction Studies
  description: >
    Motor nerve conduction velocities are normal or near-normal (>38 m/s)
    in CMT2, distinguishing it from CMT1 where velocities are significantly
    reduced (<38 m/s). Compound muscle action potential amplitudes are
    reduced, reflecting axonal loss rather than demyelination.
  notes: Key diagnostic criterion distinguishing CMT2 from CMT1
  evidence:
  - reference: PMID:16941080
    reference_title: "Comparison of CMT1A and CMT2: similarities and differences."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Median nerve motor nerve conduction velocities (MNCV) were always less than 38 m/s in CMT1A patients, whereas this was also the case in 16% of the CMT2 patients. Sensory nerve conduction velocities showed less overlap. In both CMT1A and CMT2 CMAP and SNAP amplitudes were often reduced or not obtainable in the legs."
    explanation: Comparative electrophysiology supports preserved or overlapping motor conduction velocities and reduced amplitudes as key diagnostic features separating axonal CMT2 from CMT1A.

treatments:
- name: Physical Therapy and Rehabilitation
  description: >
    Regular physical therapy to maintain muscle strength, flexibility,
    and range of motion. Includes stretching exercises, strengthening
    of unaffected muscles, and balance training.
  treatment_term:
    preferred_term: physical therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  evidence:
  - reference: PMID:40636623
    reference_title: "Clinical Characteristics of Gait Disturbance in Charcot-Marie-Tooth Disease and Future Directions in Physical Therapy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "While physical therapy may improve muscle strength and physical function, the quality of evidence remains moderate, and no standardized rehabilitation protocols have been firmly established."
    explanation: Review supports physical therapy for CMT while noting evidence quality is moderate.

- name: Orthotic Devices
  description: >
    Ankle-foot orthoses (AFOs) to compensate for foot drop and improve
    gait stability. Custom orthopedic shoes for foot deformities.
  treatment_term:
    preferred_term: orthotic supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:40636623
    reference_title: "Clinical Characteristics of Gait Disturbance in Charcot-Marie-Tooth Disease and Future Directions in Physical Therapy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Management focuses on symptomatic interventions, including orthotic support, surgical procedures, and physical therapy."
    explanation: Review confirms orthotic support as a standard management strategy for CMT.

- name: Surgical Management
  description: >
    Corrective surgery for severe foot deformities including tendon
    transfers, osteotomies, and arthrodesis. Considered when conservative
    measures fail to maintain functional ambulation.
  treatment_term:
    preferred_term: orthopedic surgical procedure
    term:
      id: NCIT:C16186
      label: Orthopedic Surgical Procedure

- name: Avoidance of Neurotoxic Medications
  description: >
    Patients should avoid medications known to worsen peripheral
    neuropathy, particularly vincristine, which can cause severe
    deterioration in CMT patients.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care

- name: Genetic Counseling
  description: >
    Genetic counseling supports inheritance-risk assessment, cascade testing,
    reproductive counseling, and interpretation of molecular diagnoses for
    families affected by genetically heterogeneous CMT2.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: MAXO:0000079
      label: genetic counseling
  evidence:
  - reference: PMID:20301532
    reference_title: "Charcot-Marie-Tooth Hereditary Neuropathy Overview."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Inform genetic counseling of family members of an individual with CMT hereditary neuropathy."
    explanation: GeneReviews explicitly includes genetic counseling for family members as part of CMT hereditary neuropathy management.

- name: Epalrestat for SORD-CMT2
  description: >
    Epalrestat is an aldose reductase inhibitor under Phase II evaluation for
    SORD-CMT2. It targets the upstream polyol pathway to reduce sorbitol
    production in patients with SORD deficiency; clinical efficacy remains
    investigational.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: epalrestat
      term:
        id: CHEBI:31539
        label: epalrestat
  target_phenotypes:
  - preferred_term: Distal muscle weakness
    term:
      id: HP:0002460
      label: Distal muscle weakness
  target_mechanisms:
  - target: SORD Deficiency and Sorbitol Accumulation
    description: >
      Epalrestat inhibits aldose reductase upstream of SORD, aiming to reduce
      sorbitol accumulation caused by SORD deficiency.
  evidence:
  - reference: clinicaltrials:NCT05777226
    reference_title: "Multi-center Study of Natural History of SORD-related Charcot-Marie-Tooth Disease and Epalrestat Treatment"
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "The primary purpose of this study is to explore the natural history of SORD-CMT2 patients by detecting the ONLS scale score and serum sorbitol level changes at 6th, 12th, 24th, and 36th months and to evaluate the effectiveness and safety of epalrestat."
    explanation: ClinicalTrials.gov documents a SORD-CMT2 epalrestat study, but results are not yet available.
  - reference: PMID:32367058
    reference_title: "Biallelic mutations in SORD cause a common and potentially treatable hereditary neuropathy with implications for diabetes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "normalized intracellular sorbitol levels in patient-derived fibroblasts"
    explanation: Patient-derived fibroblast evidence supports aldose reductase inhibition as a substrate-reduction strategy for SORD deficiency.

- name: NMD670 for CMT1/CMT2
  description: >
    NMD670 is an investigational small-molecule therapy tested in a completed
    Phase IIa placebo-controlled trial enrolling ambulatory adults with CMT1 or
    CMT2. The treatment is modeled with partial support because the trial record
    establishes clinical evaluation in CMT2 but does not provide outcome results
    in the cache.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  target_phenotypes:
  - preferred_term: Steppage gait
    term:
      id: HP:0003376
      label: Steppage gait
  - preferred_term: Distal muscle weakness
    term:
      id: HP:0002460
      label: Distal muscle weakness
  evidence:
  - reference: clinicaltrials:NCT06482437
    reference_title: "A Phase 2a, Randomised, Double-Blind, Placebo-Controlled Study to Evaluate the Efficacy, Safety, and Tolerability of NMD670 Over 21 Days in Ambulatory Adult Patients With Type 1 and Type 2 Charcot-Marie-Tooth Disease"
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "This Phase 2a study aims to evaluate the efficacy, safety and tolerability of NMD670 vs placebo administered twice a day (BID) for 21 days in ambulatory adult patients with Charcot-Marie-Tooth disease type 1 and type 2."
    explanation: ClinicalTrials.gov documents completed Phase IIa clinical evaluation of NMD670 in adults with CMT1 or CMT2, but the cache does not include efficacy results.

clinical_trials:
- name: NCT05777226
  phase: PHASE_II
  status: NOT_RECRUITING
  description: >
    Multicenter Phase II study of SORD-CMT2 natural history and epalrestat
    treatment, measuring ONLS and serum sorbitol over 36 months in about 30
    participants with SORD-CMT2.
  target_phenotypes:
  - preferred_term: Distal muscle weakness
    term:
      id: HP:0002460
      label: Distal muscle weakness
  evidence:
  - reference: clinicaltrials:NCT05777226
    reference_title: "Multi-center Study of Natural History of SORD-related Charcot-Marie-Tooth Disease and Epalrestat Treatment"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients in the drug treatment group take epalrestat (50 mg) orally three times daily."
    explanation: Trial registry evidence documents epalrestat dosing in SORD-CMT2.
  notes: ClinicalTrials.gov reports NOT_YET_RECRUITING; mapped to NOT_RECRUITING because the schema has no separate not-yet-recruiting enum.

- name: NCT06482437
  phase: PHASE_II
  status: COMPLETED
  description: >
    Phase IIa randomized, double-blind, placebo-controlled trial of NMD670 over
    21 days in ambulatory adults with genetically confirmed Charcot-Marie-Tooth
    disease type 1 or type 2.
  target_phenotypes:
  - preferred_term: Steppage gait
    term:
      id: HP:0003376
      label: Steppage gait
  - preferred_term: Distal muscle weakness
    term:
      id: HP:0002460
      label: Distal muscle weakness
  evidence:
  - reference: clinicaltrials:NCT06482437
    reference_title: "A Phase 2a, Randomised, Double-Blind, Placebo-Controlled Study to Evaluate the Efficacy, Safety, and Tolerability of NMD670 Over 21 Days in Ambulatory Adult Patients With Type 1 and Type 2 Charcot-Marie-Tooth Disease"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This Phase 2a study aims to evaluate the efficacy, safety and tolerability of NMD670 vs placebo administered twice a day (BID) for 21 days in ambulatory adult patients with Charcot-Marie-Tooth disease type 1 and type 2."
    explanation: Trial registry evidence documents a completed Phase IIa NMD670 trial that included CMT2.

datasets: []

📚

References & Deep Research

Deep Research

1

Falcon ▸

1. Disease Information

Edison Scientific Literature 44 citations 2026-04-11T12:32:46.161710

1. Disease Information

1.1 Disease overview (current understanding)

Charcot–Marie–Tooth disease (CMT) is a genetically heterogeneous inherited peripheral neuropathy characterized by length‑dependent, slowly progressive distal weakness/atrophy and sensory loss (often with pes cavus and reduced reflexes). CMT is traditionally classified by electrophysiology and pathology into demyelinating (CMT1), axonal (CMT2), and intermediate forms. (dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)

CMT2 definition (electrophysiology): * Axonal CMT2 is distinguished from demyelinating CMT1 by relatively preserved motor nerve conduction velocities (NCV/MNCV) with evidence of axonal loss (reduced amplitudes). A commonly used discriminator in the arms is NCV >38 m/s for axonal CMT2 vs <38 m/s for demyelinating CMT1. (okamoto2023thecurrentstate pages 1-2) * Alternative framework: demarcation can use ulnar motor nerve ranges: very slow <15 m/s; slow 15–35 m/s; intermediate 35–45 m/s; normal >45 m/s; axonal CMT2 typically lies in the normal/near‑normal range. (dong2024currenttreatmentmethods pages 1-2)

1.2 Key identifiers and ontology mapping

MONDO: Charcot‑Marie‑Tooth disease type 2 = MONDO:0018993 (via OpenTargets disease mapping evidence). (dong2024currenttreatmentmethods pages 2-4)
OMIM: Specific subtype example from a 2024 review: CMT2A (MFN2) = OMIM 609260. (abati2024charcot–marie‐toothtype2a pages 1-2)
MeSH / ICD‑10 / ICD‑11 / Orphanet: Not explicitly provided in retrieved full‑text excerpts for CMT2 as a parent concept; therefore, these identifiers are not populated here from primary evidence in this run.

1.3 Synonyms and alternative names

“Axonal CMT”, “axonal Charcot–Marie–Tooth disease”, and the legacy term hereditary motor and sensory neuropathy type II (HMSN II) are used in modern reviews as equivalents for CMT2. (dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)

1.4 Evidence provenance (individual vs aggregated)

Aggregated disease‑level resources: ontology mapping (MONDO via OpenTargets), review articles synthesizing many cohorts. (dong2024currenttreatmentmethods pages 2-4, dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)
Individual‑level/primary evidence: mechanistic studies in animal models and patient‑derived cells (e.g., MFN2 mutant fibroblasts; GARS1 mouse). (sleigh2023boostingperipheralbdnf pages 1-2, kumar2024mfn2coordinatesmitochondria pages 1-2)
Registry/EHR‑like data: ClinicalTrials.gov registries and large observational registries collecting patient‑reported and medical records. (NCT05902351 chunk 1)

2. Etiology

2.1 Primary causal factors

CMT2 is primarily genetic: mutations in many genes affecting axonal maintenance, mitochondrial dynamics, axonal transport, cytoskeleton, endolysosomal trafficking, and translation/protein homeostasis. (okamoto2023thecurrentstate pages 1-2, dong2024currenttreatmentmethods pages 2-4)

2.2 Genetic risk factors (causal genes; selected major subtypes)

CMT2 is genetically heterogeneous; commonly cited genes/subtypes in the retrieved evidence include: * MFN2 (CMT2A) – dominant in most cases; mitochondrial fusion/transport/ER–mitochondria tethering dysfunction. (abati2024charcot–marie‐toothtype2a pages 1-2, kumar2024mfn2coordinatesmitochondria pages 1-2) * GARS1 (CMT2D) – dominant missense with toxic gain‑of‑function interactions affecting neurotrophin signaling/axonal transport. (sleigh2023boostingperipheralbdnf pages 1-2) * NEFL (CMT2E) – neurofilament/cytoskeleton abnormalities. (dong2024currenttreatmentmethods pages 2-4) * HSPB1 (CMT2F) – mitochondrial and neurofilament transport disruption. (dong2024currenttreatmentmethods pages 2-4) * IGHMBP2 (CMT2S) – biallelic mutations affecting RNA helicase / translation pathways. (dong2024currenttreatmentmethods pages 2-4) * SORD‑related axonal neuropathy/CMT2 – biallelic loss‑of‑function; polyol pathway dysregulation with sorbitol accumulation. (estevezarias2022geneticapproachesand pages 13-16)

OpenTargets disease‑target association data support multiple CMT2‑associated targets (e.g., MFN2, MPZ, GDAP1, NEFL, HSPB1, TRPV4, DYNC1H1, AARS1) and links to curation/ClinVar evidence records. (dong2024currenttreatmentmethods pages 2-4)

2.3 Variant classes and functional consequences (examples)

SORD: 2022 review notes 14 mutations identified since initial description (May 2020), “most are frameshift or splicing mutations causing a loss of function”; a recurrent c.757delG appears in most reported patients. (estevezarias2022geneticapproachesand pages 13-16)
MFN2: CMT2A is commonly caused by dominant MFN2 mutations; a 2024 review describes a likely dominant‑negative mechanism as frequent, and highlights both loss‑ and gain‑of‑function behavior in models. (abati2024charcot–marie‐toothtype2a pages 1-2)
GARS1: 2023 mechanistic review/primary evidence frames pathogenicity as toxic gain‑of‑function due to conformational opening and aberrant interactions. (sleigh2023boostingperipheralbdnf pages 1-2)

2.4 Environmental risk factors / protective factors / gene–environment interactions

No high‑confidence, CMT2‑specific environmental risk or protective factors were identified in the retrieved sources for this run. Supportive statements focus on exercise/physical activity benefits and risks of sedentary behavior at a symptom‑management level (not disease causation). (leale2024telecoachingapotential pages 1-2)

3. Phenotypes (clinical manifestations)

3.1 Core phenotype spectrum

Common phenotype across CMT (including CMT2) includes: * Distal muscle weakness and atrophy (lower limbs first), foot drop, pes cavus/hammertoes. (okamoto2023thecurrentstate pages 1-2, dong2024currenttreatmentmethods pages 1-2) * Distal sensory loss often in a stocking–glove distribution. (okamoto2023thecurrentstate pages 1-2) * Reduced/absent tendon reflexes; gait impairment and falls. (okamoto2023thecurrentstate pages 1-2, johnson2016managementofcharcot–marie–tooth pages 4-6) * In some axonal forms, pyramidal features (e.g., extensor plantar responses, mild increased tone, preserved/increased reflexes) have been described in dominantly inherited axonal CMT2 variants. (dong2024currenttreatmentmethods pages 2-4)

3.2 Age of onset, severity, progression

CMT can present at any age; CMT2 severity ranges from severe childhood onset to milder adolescent/adult onset. (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2, okamoto2023thecurrentstate pages 1-2)
SORD‑related axonal neuropathy/CMT2: clinical homogeneity described as onset in the 2nd–3rd decade with axonal neuropathy and distal weakness/atrophy. (estevezarias2022geneticapproachesand pages 13-16)

3.3 Phenotype frequencies (where available)

Prognosis: “fewer than 5% of patients affected by CMT1 or CMT2 neuropathies become wheelchair dependent, and the majority have a normal life span.” (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2)

3.4 Quality of life (QoL) and functioning

CMT affects lifelong mobility and daily functioning; functional outcomes used in trials and rehab studies include 6‑minute walk test (6MWT), 10‑meter walk test (10MWT), Berg Balance Scale (BBS), Timed Up and Go (TUG), Overall Neuropathy Limitations Scale (ONLS), SF‑36, and disease‑specific instruments. (NCT06482437 chunk 1, tedeschi2025physicaltherapyinterventions pages 8-10)

3.5 Suggested HPO terms (not exhaustive)

Based on the phenotypes described in evidence: * Pes cavus (HP:0001760) * Hammer toe (HP:0001838) * Distal muscle weakness (HP:0002460) * Muscle atrophy (HP:0003202) * Foot drop (HP:0001762) * Hyporeflexia/Areflexia (HP:0001265 / HP:0001284) * Distal sensory impairment (e.g., Hypoesthesia, HP:0001251)

4. Genetic / Molecular Information

4.1 Causal genes (selected, evidence-backed in this run)

Key CMT2 genes/subtypes supported in retrieved evidence include MFN2 (CMT2A), GARS1 (CMT2D), NEFL (CMT2E), HSPB1 (CMT2F), IGHMBP2 (CMT2S), SORD. (dong2024currenttreatmentmethods pages 2-4, sleigh2023boostingperipheralbdnf pages 1-2, abati2024charcot–marie‐toothtype2a pages 1-2, estevezarias2022geneticapproachesand pages 13-16)

4.2 Modifier genes / oligogenicity

Direct modifier genes were not robustly characterized in the retrieved excerpts. However, recent genetics reviews emphasize “missing heritability,” structural variation, and complex inheritance in inherited peripheral neuropathies, implying potential modifiers/oligogenic contributions in some families. (NCT06482437 chunk 1)

4.3 Epigenetics and chromosomal abnormalities

No CMT2‑specific epigenetic mechanisms or chromosomal abnormalities were directly supported by the retrieved evidence in this run.

5. Environmental Information

No specific infectious or toxin causes are supported for CMT2 (a genetic neuropathy). Environmental/lifestyle considerations primarily relate to functional management (exercise, orthotics) rather than etiology. (dong2024currenttreatmentmethods pages 4-6, leale2024telecoachingapotential pages 1-2)

6. Mechanism / Pathophysiology

6.1 Mechanistic themes across CMT2

Mechanistic themes in CMT and CMT2 include disrupted axonal transport, mitochondrial dynamics, vesicle trafficking, and translation/protein synthesis processes. (okamoto2023thecurrentstate pages 1-2, dong2024currenttreatmentmethods pages 2-4)

6.2 MFN2 / CMT2A (mitochondrial dynamics, axonal transport, microtubule acetylation)

Causal chain (illustrative): MFN2 mutation → impaired mitochondrial fusion / ER–mitochondria tethering / mitochondrial transport → altered mitochondrial distribution and axonal energy/calcium/lipid homeostasis → distal axonal degeneration (length‑dependent) → distal weakness/sensory loss.

Recent mechanistic advance (2024): MFN2 coordinates mitochondrial motility with α‑tubulin acetylation by recruiting the tubulin acetyltransferase ATAT1 at mitochondria–microtubule contacts; CMT2A‑associated MFN2 mutations (R94W, T105M) alter binding and may cause axonal degeneration via dysregulated ATAT1 release and reduced acetylated tubulin. (kumar2024mfn2coordinatesmitochondria pages 1-2)

A 2024 review summarizes that MFN2 mutations disturb “the equilibrium between mitochondrial fusion and fission, of mitophagy and mitochondrial axonal transport,” and emphasizes lack of approved therapies. (abati2024charcot–marie‐toothtype2a pages 1-2)

6.3 GARS1 / CMT2D (toxic mis‑interactions; neurotrophin signaling endosome transport)

A 2023 primary study reports in vivo axonal transport disruption and a muscle‑targeted rescue concept: * Abstract quote: “CMT2D mice displayed early and persistent disturbances in axonal transport of neurotrophin-containing signaling endosomes in vivo” and “supplementation of muscles with BDNF… completely restored physiological axonal transport in neuropathic mice.” (sleigh2023boostingperipheralbdnf pages 1-2) This supports a mechanistic chain where mutant GlyRS disrupts neurotrophin receptor interactions (e.g., TrkB/BDNF axis) leading to impaired retrograde signaling endosome transport and downstream axonal pathology. (sleigh2023boostingperipheralbdnf pages 1-2)

6.4 SORD‑related axonal neuropathy (polyol pathway; sorbitol accumulation)

SORD encodes sorbitol dehydrogenase in the polyol pathway. Patient fibroblasts show complete loss of SORD protein and increased intracellular sorbitol; proposed mechanisms include osmotic stress, oxidative stress, and altered NADPH. (estevezarias2022geneticapproachesand pages 13-16)

6.5 Suggested GO biological process terms (illustrative)

Mitochondrial fusion (GO:0008053)
Mitophagy (GO:0000423)
Axonal transport (GO:0098930)
Microtubule acetylation (GO:0043473)
Retrograde axonal transport (GO:0008089)
Protein translation (GO:0006412)

6.6 Suggested Cell Ontology (CL) terms and affected cell types

Evidence emphasizes neuronal primary defects with length‑dependent vulnerability: * Peripheral motor neurons (e.g., CL:0000100 motor neuron) * Sensory neurons (e.g., CL:0000101 sensory neuron) * Schwann cells also contribute across CMT broadly (review context). (dong2024currenttreatmentmethods pages 1-2, stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2)

7. Anatomical Structures Affected

7.1 Organ/system level

Peripheral nervous system (primary) with length‑dependent distal involvement; clinical manifestations reflect degeneration of long peripheral axons. (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2, kumar2024mfn2coordinatesmitochondria pages 1-2)
Musculoskeletal system (secondary consequences): foot deformities (pes cavus/hammertoes), muscle atrophy (tibialis anterior/peroneal muscles, intrinsic hand muscles). (dong2024currenttreatmentmethods pages 1-2)

7.2 Tissue/cell level

Peripheral axons (motor and sensory), neuromuscular junction involvement in some inherited motor neuropathies (overlap). (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2, sleigh2023boostingperipheralbdnf pages 1-2)

7.3 Suggested UBERON terms (illustrative)

Peripheral nerve (UBERON:0001630)
Sciatic nerve (UBERON:0001323) (model‑system relevance). (sleigh2023boostingperipheralbdnf pages 1-2)
Skeletal muscle of lower limb (UBERON:0002389) (clinical and therapeutic relevance). (sleigh2023boostingperipheralbdnf pages 1-2)

8. Temporal Development

8.1 Onset patterns

CMT2 can begin in childhood through adulthood; severity spectrum includes early severe vs later milder disease. (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2)

8.2 Progression

Generally slowly progressive length‑dependent neuropathy; disability accumulates over time. (dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)

9. Inheritance and Population

9.1 Epidemiology (recently cited statistics)

CMT overall prevalence often cited as ~1:2,500. (dong2024currenttreatmentmethods pages 1-2)
Another review summarizes more recent prevalence figures of ~1:3,300 worldwide. (scherrer2025frominvivo pages 1-3)
A 2023 treatment review reports an “estimated incidence” of 10–40 per 100,000 individuals. (okamoto2023thecurrentstate pages 1-2)

9.2 Proportion of CMT2 and key subtypes

CMT2 share: one retrieved source states CMT2 is predicted to account for 15–30% of all CMT. (koenig2025restoringproteinsynthesis pages 21-25)
CMT2A proportion: “predominant axonal subtype… ~4–7% of all cases.” (dong2024currenttreatmentmethods pages 2-4)
Cohort breakdown (Saporta cohort summarized in 2023 review): among genetically defined cases, CMT2A (MFN2) 4%. (okamoto2023thecurrentstate pages 1-2)
Commercial lab cohort summarized in 2023 review: MFN2 4.3% of positive genetic findings; 94.9% of positives were in PMP22, GJB1, MPZ, MFN2. (okamoto2023thecurrentstate pages 1-2)

9.3 Inheritance

CMT2 includes autosomal dominant and autosomal recessive forms depending on subtype (e.g., MFN2 often dominant; SORD recessive). (dong2024currenttreatmentmethods pages 2-4, estevezarias2022geneticapproachesand pages 13-16)

10. Diagnostics

10.1 Clinical and electrophysiologic testing

Key electrophysiology concept: demyelinating vs axonal classification by motor nerve conduction velocities; axonal CMT2 tends toward preserved velocities with axonal loss signatures. (okamoto2023thecurrentstate pages 1-2, johnson2016managementofcharcot–marie–tooth pages 4-6)

10.2 Genetic testing strategies (current practice)

High‑impact recent diagnostic evidence: * Targeted NGS panels (clinical practice): In a Neurology (2020) diagnostic cohort of 220 patients, a “definite molecular diagnosis… 30%” was achieved; an additional 33% had VUS. (cortese2020targetednextgenerationsequencing pages 1-2) * Differential diagnostic yields by subtype: A Nature Reviews Neurology (2019) review reports genetic diagnosis rates: CMT1 >85%, CMT2 25–35%, HSN 30–40%, HMN 15–25%. (pipis2019nextgenerationsequencingin pages 1-5) * Four‑gene dominance: A 2020 review reports that analysis of PMP22, GJB1, MPZ, MFN2 can identify 80–90% of detectable CMT mutations, but that axonal CMT2 remains less frequently solved (10–30%). (rudnikschoneborn2020charcotmarietoothdiseaseand pages 1-2)

WES/WGS (next frontier): A high‑impact review summarizes that WGS offers ~98.4–100% coding coverage vs WES up to ~96%, and can detect structural variants with non‑exonic breakpoints; the review also notes mitochondrial sequencing should be considered because MT‑ATP6 can present as CMT2. (pipis2019nextgenerationsequencingin pages 10-14)

10.3 Differential diagnosis

Reassessment studies highlight that clinically diagnosed hereditary neuropathy can include treatable non‑genetic etiologies (e.g., inflammatory neuropathy) and benefit from comprehensive workup and sequencing, emphasizing the importance of careful differential diagnosis. (NCT06482437 chunk 1)

11. Outcomes / Prognosis

Wheelchair dependence is uncommon: “fewer than 5% … become wheelchair dependent” and most have normal lifespan. (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2)
Functional progression is variable by subtype and onset age, with severe childhood-onset forms and milder adult-onset forms. (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2)

12. Treatment

12.1 Current standard of care (real‑world implementations)

Recent 2024 treatment review statement: “Currently, there are no approved disease management methods that can fully cure patients with CMT, and rehabilitation, orthotics, and surgery are the only available treatments to ameliorate symptoms.” (dong2024currenttreatmentmethods pages 1-2)

Rehabilitation and exercise * A 2025 scoping review (search through March 2024) identified 11 studies (including 2 RCTs) of gait/balance rehab; reported improvements included, for example, 6MWT 513 m → 580 m over 8 months and 10MWT 9.2±2.1 s → 7.8±1.9 s after a 3‑week intensive program (p<0.05). (tedeschi2025physicaltherapyinterventions pages 8-10) * Orthotics: a 2024 review recommends escalation from shoe inserts to ankle‑foot orthoses (AFOs) for foot drop/calf weakness to stabilize gait and reduce pain/deformity. (dong2024currenttreatmentmethods pages 4-6)

Telecoaching / digital rehabilitation A 2024 systematic review of telecoaching in CMT screened 382 records and included 7 studies (170 patients age 11–45). It reports improvements in strength, cardiovascular ability, gait, and fatigue but emphasizes small samples and moderate study quality. Quantitative protocol details include resistance‑training intensities (e.g., 50%→70% 1RM in one study) and pediatric 24‑week programs with reported dorsiflexion benefit. (leale2024telecoachingapotential pages 2-3)

12.2 Emerging / experimental therapies relevant to CMT2

(i) Genotype‑targeted small molecule / metabolic strategy: SORD‑CMT2 * Epalrestat (aldose reductase inhibitor) is being studied in genetically confirmed SORD‑CMT2 in a Phase 2 interventional trial (China): NCT05777226 (not yet recruiting). Primary endpoints include serum sorbitol and ONLS changes over 36 months; dosing is 50 mg orally three times daily in the treatment group. (NCT05777226 chunk 1)

(ii) ASO therapy: CMT2S (IGHMBP2) * VCA‑894A intrathecal antisense oligonucleotide is being tested as an N‑of‑1 Phase 1/2 study: NCT07223632 (active not recruiting). Endpoints include safety plus functional scales (RULM, HFMSE) and a molecular endpoint (IGHMBP2 mRNA in CSF/blood). (NCT07223632 chunk 1)

(iii) Non–gene-specific symptomatic/modulator trial including CMT2 * NMD670 (SYNAPSE‑CMT; Phase 2a, randomized triple‑masked; completed): NCT06482437, with primary endpoint change in 6MWT distance after 21 days; includes genetically confirmed CMT1 or CMT2. (NCT06482437 chunk 1)

(iv) MFN2/CMT2A gene therapy concepts (preclinical) * A 2024 review emphasizes no approved therapy for CMT2A and the need for robust models. (abati2024charcot–marie‐toothtype2a pages 1-2) * A combined RNA interference + gene replacement strategy is described (patient iPSC‑derived motor neurons and mouse model delivery). Quoted from the retrieved mechanistic summary: the approach “effectively silenced the mutant MFN2 and restored functional wild-type MFN2 levels” and corrected mitochondrial distribution/mitophagy in vitro; in vivo molecular correction was shown but early toxicity in some models motivates dosing/capsid optimization. (abati2024invivoanda pages 111-114)

12.3 MAXO term suggestions (illustrative)

Physical therapy (MAXO:0000011)
Orthotic device therapy (MAXO:0000756)
Genetic counseling (MAXO:0000071)
Antisense oligonucleotide therapy (MAXO:—; depends on MAXO version)

13. Prevention

CMT2 is not preventable in the primary prevention sense (genetic etiology). Prevention is largely: * Secondary prevention: early detection via family history and genetic testing; cascade testing. * Tertiary prevention: preventing complications via orthotics, rehabilitation, fall prevention, and long‑term multidisciplinary care. (dong2024currenttreatmentmethods pages 4-6, tedeschi2025physicaltherapyinterventions pages 8-10)

14. Other Species / Natural Disease

No naturally occurring non‑human disease analogs were directly supported in the retrieved evidence for this run. However, mechanistic understanding relies heavily on engineered models and comparative biology of conserved pathways (mitochondrial dynamics, axonal transport). (abati2024charcot–marie‐toothtype2a pages 1-2)

15. Model Organisms

CMT2 mechanistic and translational work uses diverse models: * Mouse models (prominent for CMT2A) emphasized as “most versatile” for mechanistic dissection and translational studies. (abati2024charcot–marie‐toothtype2a pages 1-2) * Drosophila and zebrafish models are described for MFN2/CMT2A in vivo phenotyping and mechanism. (abati2024charcot–marie‐toothtype2a pages 1-2) * Patient‑derived iPSC motor neurons are used for genotype‑specific phenotyping and therapy testing (MFN2 RNAi+replacement approach). (abati2024invivoanda pages 111-114)

Figures and Tables (evidence-supported visuals)

A CMT classification/gene table and a schematic of molecular mechanisms were extracted from Dong et al., 2024 (Table 1 and Figure 2). These visuals consolidate subtype–gene mapping and the mechanistic categories relevant to axonal CMT2 (including MFN2/CMT2A). (dong2024currenttreatmentmethods media 63deef45, dong2024currenttreatmentmethods media 098aab8b)

Expert synthesis / analysis (authoritative perspectives)

Recent authoritative reviews converge on several points: 1. Genetic heterogeneity is the central barrier to universal CMT therapies; most treatment development is subtype‑targeted or pathway‑targeted (e.g., mitochondrial dynamics, axonal transport, translation). (okamoto2023thecurrentstate pages 1-2, dong2024currenttreatmentmethods pages 2-4) 2. Axonal CMT2 is systematically harder to genetically solve than demyelinating CMT1 in clinical practice (CMT2 ~25–35% vs CMT1 >85% genetic diagnosis in some series), motivating reanalysis, better SV detection, and WGS adoption. (pipis2019nextgenerationsequencingin pages 1-5, pipis2019nextgenerationsequencingin pages 10-14) 3. The treatment landscape for CMT2 is transitioning from purely supportive care toward genotype‑specific interventions (ASOs for CMT2S, metabolic pathway targeting for SORD‑CMT2, preclinical MFN2 gene therapy concepts), but clinical evidence remains early-stage. (NCT05777226 chunk 1, NCT07223632 chunk 1, abati2024invivoanda pages 111-114)

Key abstract-supported quotes (for knowledge base evidence items)

CMT2 (axonal) diagnostic definition: “A consistent slow NCV of < 38 m/s… represents the demyelinating form of CMT1, whereas a value >38 m/s is distinctive of the axonal form of CMT2.” (Genes 2023). (okamoto2023thecurrentstate pages 1-2)
CMT2D mechanism/therapy hypothesis: “CMT2D mice displayed early and persistent disturbances in axonal transport of neurotrophin-containing signaling endosomes in vivo” and “supplementation of muscles with BDNF… completely restored physiological axonal transport.” (JCI Insight 2023). (sleigh2023boostingperipheralbdnf pages 1-2)
MFN2/CMT2A mechanism: “MFN2 coordinates mitochondria motility with α-tubulin acetylation and this regulation is disrupted in CMT2A.” (iScience 2024). (kumar2024mfn2coordinatesmitochondria pages 1-2)

Embedded structured summary artifacts

The following tables provide a compact, knowledge‑base‑friendly summary of identifiers/definitions and the most relevant quantitative statistics and trials.

Section	Item	Details	Key evidence
Disease ID/definition	Preferred name	Charcot-Marie-Tooth disease type 2 (CMT2), an axonal form of inherited peripheral neuropathy affecting peripheral axons/neurons more than myelin (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2, dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)	Axonal hereditary neuropathy with distal weakness, sensory loss, and length-dependent degeneration (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2, dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)
Disease ID/definition	MONDO ID	MONDO:0018993 (dong2024currenttreatmentmethods pages 2-4)	Open Targets disease mapping to Charcot-Marie-Tooth disease type 2 (dong2024currenttreatmentmethods pages 2-4)
Disease ID/definition	One-line definition	Genetically heterogeneous inherited sensorimotor neuropathy in which primary pathology is axonal degeneration, typically causing slowly progressive distal weakness/atrophy, sensory loss, pes cavus, and reduced reflexes (dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)	Broad modern review definition of CMT with CMT2 as the axonal subgroup (dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)
Disease ID/definition	Key synonyms	Axonal CMT; axonal Charcot-Marie-Tooth disease; hereditary motor and sensory neuropathy type II / HMSN II (legacy terminology); inherited axonal peripheral neuropathy (dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)	Reviews classify CMT2 as the axonal subtype of CMT/HMSN (dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)
Distinguishing diagnostics	Electrophysiology threshold	Arm/forearm motor NCV/MNCV typically >38 m/s supports axonal CMT2 versus <38 m/s for demyelinating CMT1 (okamoto2023thecurrentstate pages 1-2)	“A consistent slow NCV of < 38 m/s… CMT1, whereas a value >38 m/s is distinctive of the axonal form of CMT2” (okamoto2023thecurrentstate pages 1-2)
Distinguishing diagnostics	Alternative electrophysiology framework	Ulnar motor nerve ranges: very slow <15 m/s; slow 15–35 m/s; intermediate 35–45 m/s; normal >45 m/s; CMT2 generally falls in normal/near-normal axonal range while intermediate CMT overlaps 35–45 m/s (dong2024currenttreatmentmethods pages 1-2)	Modern classification framework for inherited neuropathies (dong2024currenttreatmentmethods pages 1-2)
Distinguishing diagnostics	Clinical distinction vs CMT1	CMT2 is primarily axonal, often with preserved or only mildly slowed conduction velocities relative to CMT1, but reduced amplitudes and length-dependent distal weakness/sensory loss; CMT1 is primarily demyelinating with markedly slowed velocities (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2, dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)	Disease classification based on NCV plus primary defect (stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2, dong2024currenttreatmentmethods pages 1-2, okamoto2023thecurrentstate pages 1-2)
Common CMT2 genes/subtypes	CMT2A / MFN2	Usually AD or de novo dominant; rarer recessive or semidominant cases reported; most common axonal subtype / predominant CMT2 subtype (abati2024charcot–marie‐toothtype2a pages 1-2, dong2024currenttreatmentmethods pages 2-4, okamoto2023thecurrentstate pages 2-4)	Mitochondrial fusion/fission imbalance, mitophagy defects, impaired axonal mitochondrial transport, ER-mitochondria contact dysfunction, mtDNA/OXPHOS impairment (abati2024charcot–marie‐toothtype2a pages 1-2, dong2024currenttreatmentmethods pages 2-4, kumar2024mfn2coordinatesmitochondria pages 1-2)
Common CMT2 genes/subtypes	CMT2D / GARS1	AD dominant missense neuropathy (dong2024currenttreatmentmethods pages 2-4, sleigh2023boostingperipheralbdnf pages 1-2)	Toxic gain-of-function GlyRS conformational opening; aberrant Nrp1/VEGF signaling; TrkB/BDNF pathway disruption; impaired axonal transport; protein synthesis stress/ISR activation (dong2024currenttreatmentmethods pages 2-4, sleigh2023boostingperipheralbdnf pages 1-2)
Common CMT2 genes/subtypes	CMT2E / NEFL	Usually AD (gene repeatedly curated as a CMT2 gene) (dong2024currenttreatmentmethods pages 2-4)	Reduced neurofilament expression in cutaneous nerve fibers, altered axonal caliber, reduced conduction velocity / cytoskeletal dysfunction (dong2024currenttreatmentmethods pages 2-4)
Common CMT2 genes/subtypes	CMT2F / HSPB1	Usually AD (gene repeatedly curated as a CMT2 gene) (dong2024currenttreatmentmethods pages 2-4)	Mutant HSP27/HSPB1 lowers mitochondrial ceramide, alters mitochondrial structure/function, causes neurofilament hyperphosphorylation and impaired anterograde NF transport (dong2024currenttreatmentmethods pages 2-4)
Common CMT2 genes/subtypes	CMT2S / IGHMBP2	AR, biallelic variants (dong2024currenttreatmentmethods pages 2-4, NCT07223632 chunk 1)	ATP-dependent 5′→3′ RNA helicase dysfunction; disturbed association with ribosomal proteins, pre-rRNA processing factors, and tRNA-related species; transcription/translation defects (dong2024currenttreatmentmethods pages 2-4)
Common CMT2 genes/subtypes	SORD-related axonal neuropathy	AR, biallelic loss-of-function variants; SORD-related CMT2/dHMN (estevezarias2022geneticapproachesand pages 13-16, NCT05777226 chunk 1)	Polyol-pathway defect with sorbitol dehydrogenase loss, intracellular sorbitol accumulation, proposed osmotic/oxidative stress and NADPH depletion; c.757delG common founder-like recurrent variant (estevezarias2022geneticapproachesand pages 13-16, NCT05777226 chunk 1)
Common CMT2 genes/subtypes	Other recurrent genes highlighted in evidence	MPZ, GDAP1, MME, TRPV4, RAB7A, MORC2, DYNC1H1, AARS1 also appear among curated/associated CMT2 genes (dong2024currenttreatmentmethods pages 2-4)	Mechanistic themes across CMT2: axonal transport failure, mitochondrial dysfunction, endolysosomal trafficking defects, cytoskeletal disruption, translation defects (dong2024currenttreatmentmethods pages 2-4, okamoto2023thecurrentstate pages 1-2)

Table: This table summarizes core identifiers, diagnostic electrophysiology criteria, and the major CMT2 genes/subtypes highlighted in the evidence base. It is useful as a compact reference for disease definition, differential diagnosis from demyelinating CMT, and mechanism-oriented subtype mapping.

Item	Statistic/Design	Population	Key endpoints/outcomes	Source (include DOI/URL and year where available)	Evidence type
CMT prevalence estimate	~1:2,500 prevalence	General CMT population	Widely cited prevalence estimate for inherited CMT overall; useful upper-bound benchmark when contextualizing CMT2 burden (dong2024currenttreatmentmethods pages 1-2, scherrer2025frominvivo pages 1-3)	Biomolecules 2024, DOI: https://doi.org/10.3390/biom14091138 (2024); Journal of Tissue Engineering, DOI: https://doi.org/10.1177/20417314241310508 (2025)	Review
CMT prevalence estimate	~1:3,300 worldwide	General CMT population	More recent global prevalence estimate reported in review literature; complements older 1:2,500 estimate (scherrer2025frominvivo pages 1-3)	Journal of Tissue Engineering, DOI: https://doi.org/10.1177/20417314241310508 (2025)	Review
CMT incidence estimate	10–40 per 100,000 individuals	General CMT population	Review reports population frequency/incidence-style estimate for CMT overall; often cited in modern treatment reviews (okamoto2023thecurrentstate pages 1-2)	Genes 2023, DOI: https://doi.org/10.3390/genes14071391 (2023)	Review
CMT2 proportion among CMT	15–30% of all CMT cases	General CMT/CMT2	Axonal CMT2 estimated share of overall CMT burden (koenig2025restoringproteinsynthesis pages 21-25)	Koenig 2025, unpublished/unknown journal in retrieved context (2025)	Mechanistic study/review background
CMT2A proportion among all CMT	~4–7% of all CMT cases	General CMT; CMT2A	CMT2A identified as predominant axonal subtype; useful for subtype prioritization in diagnostics and trials (dong2024currenttreatmentmethods pages 2-4)	Biomolecules 2024, DOI: https://doi.org/10.3390/biom14091138 (2024)	Review
CMT2A proportion in genetically defined clinical cohort	4% of genetically defined CMT cases	Saporta cohort: 787/1024 diagnosed with CMT; 527 genetically defined	Among genetically defined cases: CMT1A 55%, CMTX1 15.2%, HNPP 9.2%, CMT1B 8.5%, CMT2A 4% (okamoto2023thecurrentstate pages 1-2)	Genes 2023, DOI: https://doi.org/10.3390/genes14071391 (2023)	Review citing cohort
MFN2 share among positive commercial genetic tests	4.3% of positive genetic findings	17,880 patients tested in commercial lab; 3,312 positive	PMP22 duplication/deletion predominated; MFN2 accounted for 4.3% of positive findings (okamoto2023thecurrentstate pages 1-2)	Genes 2023, DOI: https://doi.org/10.3390/genes14071391 (2023)	Review citing cohort
Gene panel diagnostic yield	30% definite molecular diagnosis	220 patients from 2 tertiary centers after targeted NGS panel	Definite diagnosis in 30%; VUS in 33%; mutations in GJB1, MFN2, MPZ comprised 39% of solved cases; CNVs in PMP22/MPZ/MFN2/SH3TC2/FDG4 also detected (cortese2020targetednextgenerationsequencing pages 1-2)	Neurology 2020, DOI: https://doi.org/10.1212/WNL.0000000000008672 (2020)	Clinical diagnostic cohort
Mutation detection rates by subtype	CMT1 >85%; CMT2 25–35%; HSN 30–40%; HMN 15–25%	Clinically diagnosed inherited neuropathy subgroups	Demonstrates markedly lower solve rate in axonal CMT2 than demyelinating CMT1, supporting broader sequencing and reanalysis (pipis2019nextgenerationsequencingin pages 1-5)	Nat Rev Neurol 2019, DOI: https://doi.org/10.1038/s41582-019-0254-5 (2019)	Review
Mutation detection rates by subtype (alternative summary)	CMT1 up to ~80%; CMT2 ~10–30%	CMT subgroups	Four-gene testing (PMP22, GJB1, MPZ, MFN2) identifies 80–90% of detectable mutations overall, but axonal CMT2 remains much harder to solve genetically (rudnikschoneborn2020charcotmarietoothdiseaseand pages 1-2)	Medizinische Genetik 2020, DOI: https://doi.org/10.1515/medgen-2020-2038 (2020)	Review
WES/WGS strategy	WES yield 19–45% in previously negative cases; WGS offers ~98.4–100% coding coverage vs WES up to ~96%	Unsolved CMT cohorts	WGS can detect structural variants and improve coverage; mitochondrial sequencing should be considered because MT-ATP6 can present as CMT2 (pipis2019nextgenerationsequencingin pages 10-14, pipis2019nextgenerationsequencingin pages 5-10)	Nat Rev Neurol 2019, DOI: https://doi.org/10.1038/s41582-019-0254-5 (2019)	Review
NCT05777226: epalrestat in SORD-CMT2	Phase 2; multicenter; non-randomized; parallel; open-label; estimated n=30	Genetically confirmed SORD-CMT2, age >14 to ≤50 years	Epalrestat 50 mg orally three times daily for 36 months vs no intervention; primary endpoints: serum sorbitol and ONLS change; secondary: 10MWRT (NCT05777226 chunk 1)	ClinicalTrials.gov NCT05777226, https://clinicaltrials.gov/study/NCT05777226 (posted 2023-03-21; updated 2023-04-18)	Clinical trial registry
NCT06482437: NMD670 in CMT1/CMT2	Phase 2a; randomized; triple-masked; placebo-controlled; completed; n=81	Ambulatory adults with genetically confirmed CMT type 1 or 2	NMD670 tablets twice daily for 21 days; primary endpoint: change in 6MWT distance; secondary endpoints include CMT-FOM, 10MW/RT, fatigue index, ONLS, CMT-HI, SF-36, jitter/blocking, safety (NCT06482437 chunk 1)	ClinicalTrials.gov NCT06482437, https://clinicaltrials.gov/study/NCT06482437 (2024)	Clinical trial registry
NCT07223632: VCA-894A in CMT2S	Phase 1/2; N-of-1; open-label; single-center; active-not-recruiting; n=1	Genetically confirmed CMT2S with IGHMBP2 c.1235+894C>A	Intrathecal ASO VCA-894A; primary endpoints: safety, RULM change, HFMSE change; secondary: IGHMBP2 mRNA rescue in CSF/blood (NCT07223632 chunk 1)	ClinicalTrials.gov NCT07223632, https://clinicaltrials.gov/study/NCT07223632 (first posted 2025-11-03)	Clinical trial registry
MFN2/CMT2A RNAi + gene replacement	Preclinical combined RNAi + gene replacement; AAV9 CSF delivery in mouse model; iPSC motor neurons in vitro	CMT2A patient-specific iPSC-derived motor neurons; MitoCharc1 mouse / MFN2 models	Silenced endogenous mutant MFN2 and restored WT MFN2; rescued altered axonal mitochondrial distribution and abnormal mitophagy in vitro; molecular correction confirmed in vivo, but toxicity concerns noted in some models (abati2024invivoanda pages 111-114, abati2024invivoand pages 111-114)	Cell Mol Life Sci 2023, DOI: https://doi.org/10.1007/s00018-023-05018-w (2023); Abati thesis/context 2024	Mechanistic study
Rehabilitation / supportive management relevant to CMT2	Multimodal rehab; orthotics; no approved curative pharmacotherapy	Broad CMT population including CMT2	Reviews emphasize rehabilitation, orthotics, and surgery as current mainstay symptom management; tailored exercise may improve gait, balance, fatigue, and QoL (dong2024currenttreatmentmethods pages 1-2, tedeschi2025physicaltherapyinterventions pages 8-10, dong2024currenttreatmentmethods pages 4-6)	Biomolecules 2024, DOI: https://doi.org/10.3390/biom14091138 (2024); Life 2025, DOI: https://doi.org/10.3390/life15071036 (2025)	Review / scoping review

Table: This table summarizes the key numerical burden estimates, diagnostic yields, and active or recent therapy studies most relevant to Charcot-Marie-Tooth disease type 2. It is useful for quickly comparing population statistics, genetic testing performance, and the current interventional landscape for CMT2 subtypes.

References

(dong2024currenttreatmentmethods pages 1-2): Hongxian Dong, Boquan Qin, Hui Zhang, Lei Lei, and Shizhou Wu. Current treatment methods for charcot–marie–tooth diseases. Biomolecules, 14:1138, Sep 2024. URL: https://doi.org/10.3390/biom14091138, doi:10.3390/biom14091138. This article has 9 citations.
(okamoto2023thecurrentstate pages 1-2): Yuji Okamoto and Hiroshi Takashima. The current state of charcot–marie–tooth disease treatment. Genes, 14:1391, Jul 2023. URL: https://doi.org/10.3390/genes14071391, doi:10.3390/genes14071391. This article has 56 citations.
(dong2024currenttreatmentmethods pages 2-4): Hongxian Dong, Boquan Qin, Hui Zhang, Lei Lei, and Shizhou Wu. Current treatment methods for charcot–marie–tooth diseases. Biomolecules, 14:1138, Sep 2024. URL: https://doi.org/10.3390/biom14091138, doi:10.3390/biom14091138. This article has 9 citations.
(abati2024charcot–marie‐toothtype2a pages 1-2): Elena Abati, Mafalda Rizzuti, Alessia Anastasia, Giacomo Pietro Comi, Stefania Corti, and Federica Rizzo. Charcot–marie‐tooth type 2a in vivo models: current updates. Journal of Cellular and Molecular Medicine, May 2024. URL: https://doi.org/10.1111/jcmm.18293, doi:10.1111/jcmm.18293. This article has 6 citations and is from a peer-reviewed journal.
(sleigh2023boostingperipheralbdnf pages 1-2): James N. Sleigh, David Villarroel-Campos, Sunaina Surana, Tahmina Wickenden, Yao Tong, Rebecca L. Simkin, Jose Norberto S. Vargas, Elena R. Rhymes, Andrew P. Tosolini, Steven J. West, Qian Zhang, Xiang-Lei Yang, and Giampietro Schiavo. Boosting peripheral bdnf rescues impaired in vivo axonal transport in cmt2d mice. JCI Insight, May 2023. URL: https://doi.org/10.1172/jci.insight.157191, doi:10.1172/jci.insight.157191. This article has 24 citations and is from a domain leading peer-reviewed journal.
(kumar2024mfn2coordinatesmitochondria pages 1-2): Atul Kumar, Delfina Larrea, Maria Elena Pero, Paola Infante, Marilisa Conenna, Grace J. Shin, Vincent Van Elias, Wesley B. Grueber, Lucia Di Marcotullio, Estela Area-Gomez, and Francesca Bartolini. Mfn2 coordinates mitochondria motility with α-tubulin acetylation and this regulation is disrupted in cmt2a. iScience, 27:109994, Jun 2024. URL: https://doi.org/10.1016/j.isci.2024.109994, doi:10.1016/j.isci.2024.109994. This article has 13 citations and is from a peer-reviewed journal.
(NCT05902351 chunk 1): Natural History Study for Charcot Marie Tooth Disease. Hereditary Neuropathy Foundation. 2013. ClinicalTrials.gov Identifier: NCT05902351
(estevezarias2022geneticapproachesand pages 13-16): Berta Estévez-Arias, Laura Carrera-García, Andrés Nascimento, Lara Cantarero, Janet Hoenicka, and Francesc Palau. Genetic approaches and pathogenic pathways in the clinical management of charcot-marie-tooth disease. Journal of Translational Genetics and Genomics, 6:333-352, Jan 2022. URL: https://doi.org/10.20517/jtgg.2022.04, doi:10.20517/jtgg.2022.04. This article has 11 citations.
(leale2024telecoachingapotential pages 1-2): Ignazio Leale, Vincenzo Di Stefano, Carola Costanza, Filippo Brighina, Michele Roccella, Antonio Palma, and Giuseppe Battaglia. Telecoaching: a potential new training model for charcot-marie-tooth patients: a systematic review. Frontiers in Neurology, May 2024. URL: https://doi.org/10.3389/fneur.2024.1359091, doi:10.3389/fneur.2024.1359091. This article has 12 citations and is from a peer-reviewed journal.
(johnson2016managementofcharcot–marie–tooth pages 4-6): Nicholas Johnson, Donald McCorquodale, and Evan Pucillo. Management of charcot–marie–tooth disease: improving long-term care with a multidisciplinary approach. Journal of Multidisciplinary Healthcare, 9:7-19, Jan 2016. URL: https://doi.org/10.2147/jmdh.s69979, doi:10.2147/jmdh.s69979. This article has 101 citations and is from a peer-reviewed journal.
(stavrou2023charcot–marie–toothneuropathiescurrentgene pages 2-2): Marina Stavrou, Alexia Kagiava, Irene Sargiannidou, Elena Georgiou, and Kleopas A. Kleopa. charcot–marie–toothneuropathies: current gene therapy advances and the route toward translation. Journal of the Peripheral Nervous System, 28:150-168, Apr 2023. URL: https://doi.org/10.1111/jns.12543, doi:10.1111/jns.12543. This article has 27 citations and is from a peer-reviewed journal.
(NCT06482437 chunk 1): Safety and Efficacy of NMD670 in Adult Patients With Type 1 and Type 2 Charcot-Marie-Tooth Disease. NMD Pharma A/S. 2024. ClinicalTrials.gov Identifier: NCT06482437
(tedeschi2025physicaltherapyinterventions pages 8-10): Roberto Tedeschi, Danilo Donati, and Federica Giorgi. Physical therapy interventions for gait and balance in charcot-marie-tooth disease: a scoping review. Life, 15:1036, Jun 2025. URL: https://doi.org/10.3390/life15071036, doi:10.3390/life15071036. This article has 2 citations.
(dong2024currenttreatmentmethods pages 4-6): Hongxian Dong, Boquan Qin, Hui Zhang, Lei Lei, and Shizhou Wu. Current treatment methods for charcot–marie–tooth diseases. Biomolecules, 14:1138, Sep 2024. URL: https://doi.org/10.3390/biom14091138, doi:10.3390/biom14091138. This article has 9 citations.
(scherrer2025frominvivo pages 1-3): Camille Scherrer, Camille Loret, Nicolas Védrenne, Colman Buckley, Anne-Sophie Lia, Vincent Kermene, Franck Sturtz, Frédéric Favreau, Amandine Rovini, and Pierre-Antoine Faye. From in vivo models to in vitro bioengineered neuromuscular junctions for the study of charcot-marie-tooth disease. Journal of Tissue Engineering, Mar 2025. URL: https://doi.org/10.1177/20417314241310508, doi:10.1177/20417314241310508. This article has 0 citations and is from a domain leading peer-reviewed journal.
(koenig2025restoringproteinsynthesis pages 21-25): J Koenig. Restoring protein synthesis in a neuronal model of charcot-marie-tooth disease. Unknown journal, 2025.
(cortese2020targetednextgenerationsequencing pages 1-2): Andrea Cortese, Janel E. Wilcox, James M. Polke, Roy Poh, Mariola Skorupinska, Alexander M. Rossor, Matilde Laura, Pedro J. Tomaselli, Henry Houlden, Michael E. Shy, and Mary M. Reilly. Targeted next-generation sequencing panels in the diagnosis of charcot-marie-tooth disease. Neurology, Jan 2020. URL: https://doi.org/10.1212/wnl.0000000000008672, doi:10.1212/wnl.0000000000008672. This article has 125 citations and is from a highest quality peer-reviewed journal.
(pipis2019nextgenerationsequencingin pages 1-5): Menelaos Pipis, Alexander M. Rossor, Matilde Laura, and Mary M. Reilly. Next-generation sequencing in charcot–marie–tooth disease: opportunities and challenges. Nature Reviews Neurology, 15:644-656, Oct 2019. URL: https://doi.org/10.1038/s41582-019-0254-5, doi:10.1038/s41582-019-0254-5. This article has 243 citations and is from a highest quality peer-reviewed journal.
(rudnikschoneborn2020charcotmarietoothdiseaseand pages 1-2): Sabine Rudnik-Schöneborn, Michaela Auer-Grumbach, and Jan Senderek. Charcot-marie-tooth disease and hereditary motor neuropathies – update 2020. Medizinische Genetik, 32:207-219, Sep 2020. URL: https://doi.org/10.1515/medgen-2020-2038, doi:10.1515/medgen-2020-2038. This article has 37 citations.
(pipis2019nextgenerationsequencingin pages 10-14): Menelaos Pipis, Alexander M. Rossor, Matilde Laura, and Mary M. Reilly. Next-generation sequencing in charcot–marie–tooth disease: opportunities and challenges. Nature Reviews Neurology, 15:644-656, Oct 2019. URL: https://doi.org/10.1038/s41582-019-0254-5, doi:10.1038/s41582-019-0254-5. This article has 243 citations and is from a highest quality peer-reviewed journal.
(leale2024telecoachingapotential pages 2-3): Ignazio Leale, Vincenzo Di Stefano, Carola Costanza, Filippo Brighina, Michele Roccella, Antonio Palma, and Giuseppe Battaglia. Telecoaching: a potential new training model for charcot-marie-tooth patients: a systematic review. Frontiers in Neurology, May 2024. URL: https://doi.org/10.3389/fneur.2024.1359091, doi:10.3389/fneur.2024.1359091. This article has 12 citations and is from a peer-reviewed journal.
(NCT05777226 chunk 1): Ruxu Zhang. Research of SORD-CMT Natural History and Epalrestat Treatment. The Third Xiangya Hospital of Central South University. 2023. ClinicalTrials.gov Identifier: NCT05777226
(NCT07223632 chunk 1): Treatment of Charcot-Marie-Tooth Disease, Axonal, Type 2S (CMT2S) in an Individual Patient. Vanda Pharmaceuticals. 2025. ClinicalTrials.gov Identifier: NCT07223632
(abati2024invivoanda pages 111-114): E Abati. In vivo and in vitro evaluation of the combination of rna interfering and gene therapy for treating mitofusin2-related diseases. Unknown journal, 2024.
(dong2024currenttreatmentmethods media 63deef45): Hongxian Dong, Boquan Qin, Hui Zhang, Lei Lei, and Shizhou Wu. Current treatment methods for charcot–marie–tooth diseases. Biomolecules, 14:1138, Sep 2024. URL: https://doi.org/10.3390/biom14091138, doi:10.3390/biom14091138. This article has 9 citations.
(dong2024currenttreatmentmethods media 098aab8b): Hongxian Dong, Boquan Qin, Hui Zhang, Lei Lei, and Shizhou Wu. Current treatment methods for charcot–marie–tooth diseases. Biomolecules, 14:1138, Sep 2024. URL: https://doi.org/10.3390/biom14091138, doi:10.3390/biom14091138. This article has 9 citations.
(okamoto2023thecurrentstate pages 2-4): Yuji Okamoto and Hiroshi Takashima. The current state of charcot–marie–tooth disease treatment. Genes, 14:1391, Jul 2023. URL: https://doi.org/10.3390/genes14071391, doi:10.3390/genes14071391. This article has 56 citations.
(pipis2019nextgenerationsequencingin pages 5-10): Menelaos Pipis, Alexander M. Rossor, Matilde Laura, and Mary M. Reilly. Next-generation sequencing in charcot–marie–tooth disease: opportunities and challenges. Nature Reviews Neurology, 15:644-656, Oct 2019. URL: https://doi.org/10.1038/s41582-019-0254-5, doi:10.1038/s41582-019-0254-5. This article has 243 citations and is from a highest quality peer-reviewed journal.
(abati2024invivoand pages 111-114): E Abati. In vivo and in vitro evaluation of the combination of rna interfering and gene therapy for treating mitofusin2-related diseases. Unknown journal, 2024.

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Inheritance

Subtypes

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Treatments

Clinical Trials

Source YAML

References & Deep Research

Deep Research

1. Disease Information

1.1 Disease overview (current understanding)

1.2 Key identifiers and ontology mapping

1.3 Synonyms and alternative names

1.4 Evidence provenance (individual vs aggregated)

2. Etiology

2.1 Primary causal factors

2.2 Genetic risk factors (causal genes; selected major subtypes)

2.3 Variant classes and functional consequences (examples)

2.4 Environmental risk factors / protective factors / gene–environment interactions

3. Phenotypes (clinical manifestations)

3.1 Core phenotype spectrum

3.2 Age of onset, severity, progression

3.3 Phenotype frequencies (where available)

3.4 Quality of life (QoL) and functioning

3.5 Suggested HPO terms (not exhaustive)

4. Genetic / Molecular Information

4.1 Causal genes (selected, evidence-backed in this run)

4.2 Modifier genes / oligogenicity

4.3 Epigenetics and chromosomal abnormalities

5. Environmental Information

6. Mechanism / Pathophysiology

6.1 Mechanistic themes across CMT2

6.2 MFN2 / CMT2A (mitochondrial dynamics, axonal transport, microtubule acetylation)

6.3 GARS1 / CMT2D (toxic mis‑interactions; neurotrophin signaling endosome transport)

6.4 SORD‑related axonal neuropathy (polyol pathway; sorbitol accumulation)

6.5 Suggested GO biological process terms (illustrative)

6.6 Suggested Cell Ontology (CL) terms and affected cell types

7. Anatomical Structures Affected

7.1 Organ/system level

7.2 Tissue/cell level

7.3 Suggested UBERON terms (illustrative)

8. Temporal Development

8.1 Onset patterns

8.2 Progression

9. Inheritance and Population

9.1 Epidemiology (recently cited statistics)

9.2 Proportion of CMT2 and key subtypes

9.3 Inheritance

10. Diagnostics

10.1 Clinical and electrophysiologic testing

10.2 Genetic testing strategies (current practice)

10.3 Differential diagnosis

11. Outcomes / Prognosis

12. Treatment

12.1 Current standard of care (real‑world implementations)

12.2 Emerging / experimental therapies relevant to CMT2

12.3 MAXO term suggestions (illustrative)

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Figures and Tables (evidence-supported visuals)

Expert synthesis / analysis (authoritative perspectives)

Key abstract-supported quotes (for knowledge base evidence items)

Embedded structured summary artifacts