Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients Caregivers Providers
Log In Ask a Question
PubMed This is a summary of 21 peer-reviewed journal articles Updated
Neurology · Hereditary Peripheral Neuropathy

The Biology of Genetic Neuropathy: Why Nerves Struggle

At a Glance

Genetic peripheral neuropathy is caused by DNA mutations that damage either a nerve's protective coating (myelin) or its inner wire (axon). Major subtypes like CMT, HNPP, and hATTR disrupt nerve signals, leading to symptoms like numbness, weakness, and pain that typically begin in the feet.

Hereditary peripheral neuropathy is a group of genetic conditions that affect the peripheral nerves—the “wiring” that connects your brain and spinal cord to the rest of your body. Unlike acquired neuropathies, which are caused by external factors like diabetes, vitamin deficiencies, or toxins, genetic neuropathies are caused by a permanent change (mutation) in your DNA [1][2]. These mutations interfere with how nerves are built, maintained, or how they send signals to your muscles and skin.

The Two Main Biological Mechanisms

To understand how genetic neuropathy works, it helps to think of a nerve like an electrical cable. The cable has a central copper wire (the axon) and a protective plastic coating (the myelin sheath).

1. Damage to the Coating (Demyelinating)

In some genetic neuropathies, the primary problem is with the Schwann cells, which are the specialized cells responsible for making and maintaining the myelin sheath [3]. When the myelin is thin, patchy, or broken, the electrical signals traveling along the nerve slow down significantly [4]. Over time, this poor insulation can also lead to the “wire” underneath becoming damaged [5].

2. Damage to the Wire (Axonal)

In other types, the problem starts directly within the axon itself [6]. This often happens because the nerve cell cannot effectively transport essential nutrients, energy-producing mitochondria, or proteins down the long “wire” to the hands and feet [7][8]. Because the longest nerves are the hardest to maintain, symptoms typically start in the feet and move upward—a pattern called length-dependent degeneration [9].

Major Genetic Subtypes

Charcot-Marie-Tooth (CMT) Disease

CMT is the most common form of inherited neuropathy, affecting approximately 1 in 2,500 people [10]. It is divided into two main categories based on the biological mechanisms described above:

  • CMT1 (Demyelinating): Caused by defects in the myelin sheath. The most common version, CMT1A, happens when a person has an extra copy of the PMP22 gene [11]. This “overdose” of protein prevents the Schwann cells from coating the nerve correctly [12].
  • CMT2 (Axonal): Caused by direct damage to the axon. The myelin is usually fine, but the nerve fiber itself breaks down, often due to mutations in genes like MFN2, which helps manage the cell’s energy [8][13].

Hereditary Neuropathy with liability to Pressure Palsies (HNPP)

While CMT1A is caused by an extra copy of the PMP22 gene, HNPP is caused by a missing copy (deletion) of the same gene [12]. This lack of protein makes nerves extremely sensitive to physical pressure [14]. Under a microscope, the myelin shows “sausage-like” swellings called tomacula [15]. People with HNPP may experience temporary numbness or weakness (palsy) simply from leaning on an elbow or crossing their legs [14].

Hereditary Sensory and Autonomic Neuropathy (HSAN)

HSAN is a rarer group of disorders that primarily target the nerves responsible for feeling pain and temperature (sensory) and controlling internal functions like blood pressure (autonomic) [9]. Because it affects the tiny, unmyelinated nerve fibers first, doctors may refer to this as a Small Fiber Neuropathy [9]. The biological cause often involves defects in the “skeleton” of the nerve cell or the way the cell handles certain fats (lipids) [16][17].

Hereditary ATTR (hATTR) Amyloidosis

Also known as FAP (Familial Amyloid Polyneuropathy), this condition is biologically unique. It is caused by mutations in the TTR gene, which makes a protein called transthyretin [18]. In this disease, the protein misfolds and forms “clumps” called amyloid that deposit directly on the nerves [19]. These deposits are toxic and physically damage the nerve fibers. Like HSAN, it frequently presents initially as a Small Fiber Neuropathy with burning pain, before progressing to affect the heart and digestive system [20][21].

Summary of Subtypes

Subtype Primary Biological Target Key Gene Example Typical Mechanism
CMT1 Myelin Sheath PMP22 (Duplication) Slowed signal speed due to poor insulation [11]
CMT2 Axon (The “Wire”) MFN2 Nerve fiber breakdown due to transport/energy failure [8]
HNPP Myelin Sheath PMP22 (Deletion) Pressure sensitivity due to myelin swellings (tomacula) [14]
HSAN Sensory/Autonomic Axons SPTLC1 Loss of pain/temp sensation due to lipid or structural defects [17]
hATTR Global Nerve Tissue TTR Toxic protein clumps (amyloid) damaging the nerves [18]

Common questions in this guide

What is the difference between demyelinating and axonal neuropathy?
Demyelinating neuropathy means the protective coating (myelin) around your nerves is damaged, which slows down electrical signals. Axonal neuropathy means the inner nerve fiber itself (the axon) is breaking down, making it difficult for the nerve to transport nutrients.
Why do genetic neuropathy symptoms typically start in the feet?
Nerves that reach down to your feet are the longest in your body and are the hardest to maintain. When a genetic mutation makes it difficult to transport nutrients along the nerve, these long nerves are usually the first to struggle, a pattern called length-dependent degeneration.
How does the PMP22 gene affect my nerves?
The PMP22 gene provides instructions for making the protective coating around your nerves. If you have an extra copy of this gene, it causes CMT1A by disrupting the coating. If you are missing a copy, it causes HNPP, which makes nerves extremely sensitive to normal physical pressure.
Why does leaning on my elbows or crossing my legs cause numbness?
If you have Hereditary Neuropathy with liability to Pressure Palsies (HNPP), your nerves lack proper insulation due to a missing gene. This makes them highly sensitive to physical pressure, meaning simple actions like leaning on an elbow or crossing your legs can trigger temporary numbness or weakness.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What was the result of my nerve conduction study, and did it show 'slowed' signals (myelin damage) or 'weak' signals (axon damage)?
  2. 2.Based on my genetic testing, which specific gene mutation do I have, and how does it affect my nerves?
  3. 3.Do I have the 'duplication' or the 'deletion' of the PMP22 gene, and what does that mean for my long-term symptoms?
  4. 4.Is my neuropathy 'length-dependent,' and how does that influence where I feel symptoms first?
  5. 5.Are there specific physical triggers, like pressure on certain limbs, that I should avoid based on my subtype?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (21)
  1. 1

    Hearing loss in inherited peripheral neuropathies: Molecular diagnosis by NGS in a French series.

    Lerat J, Magdelaine C, Roux AF, et al.

    Molecular genetics & genomic medicine 2019; (7(9)):e839 doi:10.1002/mgg3.839.

    PMID: 31393079
  2. 2

    Charcot-Marie-Tooth disease misdiagnosed as chronic inflammatory demyelinating polyradiculoneuropathy: An international multicentric retrospective study.

    Hauw F, Fargeot G, Adams D, et al.

    European journal of neurology 2021; (28(9)):2846-2854 doi:10.1111/ene.14950.

    PMID: 34060689
  3. 3

    Identification of Candidate Genes Associated with Charcot-Marie-Tooth Disease by Network and Pathway Analysis.

    Zhong M, Luo Q, Ye T, et al.

    BioMed research international 2020; (2020()):1353516 doi:10.1155/2020/1353516.

    PMID: 33029488
  4. 4

    Establishment of an In Vitro Disease Model of Charcot-Marie-Tooth Disease using Human Induced Pluripotent Stem Cells.

    Liu X, Ishikawa KI, Hattori N, Akamatsu W

    Juntendo medical journal 2025; (71(3)):156-157 doi:10.14789/ejmj.JMJ24-0046-R.

    PMID: 40666492
  5. 5

    PMP22 antisense oligonucleotides reverse Charcot-Marie-Tooth disease type 1A features in rodent models.

    Zhao HT, Damle S, Ikeda-Lee K, et al.

    The Journal of clinical investigation 2018; (128(1)):359-368.

    PMID: 29202483
  6. 6

    Mechanisms and treatment strategies of demyelinating and dysmyelinating Charcot-Marie-Tooth disease.

    Hertzog N, Jacob C

    Neural regeneration research 2023; (18(9)):1931-1939 doi:10.4103/1673-5374.367834.

    PMID: 36926710
  7. 7

    Novel HDAC6 Inhibitors Increase Tubulin Acetylation and Rescue Axonal Transport of Mitochondria in a Model of Charcot-Marie-Tooth Type 2F.

    Adalbert R, Kaieda A, Antoniou C, et al.

    ACS chemical neuroscience 2020; (11(3)):258-267 doi:10.1021/acschemneuro.9b00338.

    PMID: 31845794
  8. 8

    HDAC6 inhibitors: Translating genetic and molecular insights into a therapy for axonal CMT.

    Rossaert E, Van Den Bosch L

    Brain research 2020; (1733()):146692 doi:10.1016/j.brainres.2020.146692.

    PMID: 32006555
  9. 9

    A neuropathy-associated kinesin KIF1A mutation hyper-stabilizes the motor-neck interaction during the ATPase cycle.

    Morikawa M, Jerath NU, Ogawa T, et al.

    The EMBO journal 2022; (41(5)):e108899 doi:10.15252/embj.2021108899.

    PMID: 35132656
  10. 10

    Loss of YAP in Schwann cells improves HNPP pathophysiology.

    Moore SM, Jeong E, Zahid M, et al.

    Glia 2024; (72(11)):1974-1984 doi:10.1002/glia.24592.

    PMID: 38989661
  11. 11

    Aberrant Molecular Myelin Architecture in Charcot-Marie-Tooth Disease Type 1A and Hereditary Neuropathy With Liability to Pressure Palsies.

    Moss KR, Arowolo MA, Gutierrez DR, Höke A

    Glia 2026; (74(2)):e70124 doi:10.1002/glia.70124.

    PMID: 41400104
  12. 12

    Peripheral Myelin Protein 22 Gene Mutations in Charcot-Marie-Tooth Disease Type 1E Patients.

    Jung NY, Kwon HM, Nam DE, et al.

    Genes 2022; (13(7)) doi:10.3390/genes13071219.

    PMID: 35886002
  13. 13

    Evaluation of Pathogenicity and Causativity of Variants in the MPZ and SH3TC2 Genes in a Family Case of Hereditary Peripheral Neuropathy.

    Shchagina O, Orlova M, Murtazina A, et al.

    International journal of molecular sciences 2023; (24(12)) doi:10.3390/ijms24129786.

    PMID: 37372933
  14. 14

    Targeting PI3K/Akt/mTOR signaling in rodent models of PMP22 gene-dosage diseases.

    Krauter D, Stausberg D, Hartmann TJ, et al.

    EMBO molecular medicine 2024; (16(3)):616-640 doi:10.1038/s44321-023-00019-5.

    PMID: 38383802
  15. 15

    Hereditary neuropathy with liability to pressure palsies.

    Attarian S, Fatehi F, Rajabally YA, Pareyson D

    Journal of neurology 2020; (267(8)):2198-2206 doi:10.1007/s00415-019-09319-8.

    PMID: 30989370
  16. 16

    Hereditary Sensory and Autonomic Neuropathy Type II in a Female Child with Multiple Orthopaedic Ailments: Diagnosis and Operative Management.

    Kamath SU, Krishnamurthy SL, Annappa R

    Indian journal of orthopaedics 2022; (56(8)):1482-1487 doi:10.1007/s43465-022-00671-y.

    PMID: 35928661
  17. 17

    Recessive mutations in the neuronal isoforms of DST, encoding dystonin, lead to abnormal actin cytoskeleton organization and HSAN type VI.

    Fortugno P, Angelucci F, Cestra G, et al.

    Human mutation 2019; (40(1)):106-114 doi:10.1002/humu.23678.

    PMID: 30371979
  18. 18

    Targeted Therapies for Hereditary Peripheral Neuropathies: Systematic Review and Steps Towards a 'treatabolome'.

    Jennings MJ, Lochmüller A, Atalaia A, Horvath R

    Journal of neuromuscular diseases 2021; (8(3)):383-400 doi:10.3233/JND-200546.

    PMID: 32773395
  19. 19

    Neuromuscular amyloidosis: Unmasking the master of disguise.

    Pinto MV, Dyck PJB, Liewluck T

    Muscle & nerve 2021; (64(1)):23-36 doi:10.1002/mus.27150.

    PMID: 33458861
  20. 20

    "Red-flag" symptom clusters in transthyretin familial amyloid polyneuropathy.

    Conceição I, González-Duarte A, Obici L, et al.

    Journal of the peripheral nervous system : JPNS 2016; (21(1)):5-9 doi:10.1111/jns.12153.

    PMID: 26663427
  21. 21

    [State of corneal nerve fibers in systemic amyloidosis].

    Avetisov SE, Surnina ZV, Zinovyeva OE, et al.

    Vestnik oftalmologii 2021; (137(5. Vyp. 2)):231-237 doi:10.17116/oftalma2021137052231.

    PMID: 34669332

This page explains the biological mechanisms of genetic neuropathy for educational purposes. Always consult your neurologist or genetic counselor for interpreting your specific genetic test results and diagnosis.

Get notified when new evidence is published on Genetic peripheral neuropathy.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.