Overview
Understanding what causes Small Fiber Neuropathy can help you and your doctor
create the best treatment plan. Many different things can damage the small
nerve fibers in your body. Sometimes it's one clear cause, and sometimes
it's a combination of factors.
In about 53% of cases, doctors can't find a specific cause
even after thorough testing. This is called "idiopathic" small fiber neuropathy.
Even when the cause isn't clear, treatments can still help
manage your symptoms.
Finding the cause is important because treating the underlying condition
can sometimes slow down or stop more nerve damage so keep pushing for more testing if your
small fiber neuropathy has been labeled "idiopathic". Idiopathic ultimately means doctors have not
found the cause...yet. Diabetes is the most common identifiable cause, but there are many other
possibilities your doctor will check for.
Diabetes and Blood Sugar
Diabetes is by far the most common cause of small fiber neuropathy.
High blood sugar levels over time can damage the small
nerve fibers, especially in your feet and hands. This happens
because excess sugar in your blood can harm the tiny blood vessels that
feed your nerves.
Impaired glucose tolerance and components of metabolic
syndrome are often associated with small fiber neuropathy. This
means even pre-diabetes or insulin resistance can start damaging your nerves.
- Type 1 Diabetes - Usually develops in childhood or young adulthood when the body stops making insulin
- Type 2 Diabetes - More common form that usually develops in adults when the body doesn't use insulin properly
- Pre-diabetes - Blood sugar levels higher than normal but not yet diabetic (HbA1c 5.7-6.4%)
- Metabolic Syndrome - A group of conditions including high blood pressure, excess belly fat, and abnormal cholesterol levels
- Latent Autoimmune Diabetes in Adults (LADA) - A slow-developing form of autoimmune diabetes in adults
The good news is that better blood sugar control can help prevent more
nerve damage and sometimes even improve symptoms. Work with your healthcare
team to keep your blood sugar in the target range they recommend for you.
Autoimmune Conditions
Autoimmune diseases are associated with small fiber
neuropathy, though the exact way they cause nerve damage isn't
always clear. In autoimmune conditions, your immune system mistakenly attacks
healthy parts of your body, including your nerves.
These conditions can cause inflammation that damages the small nerve
fibers or affects the blood vessels that supply them. Some autoimmune
conditions are more likely to cause neuropathy than others.
- Sarcoidosis - A condition causing inflammation in various organs. Up to 40% of sarcoidosis patients develop small fiber neuropathy
- Sjögren's Syndrome - Affects glands that make tears and saliva, but can also damage nerves
- Systemic Lupus Erythematosus (SLE) - Can affect many body systems including the nervous system
- Celiac Disease - Sensitivity to gluten that can cause nerve damage in some people
- Rheumatoid Arthritis - Joint inflammation that can sometimes affect nerves too
- Inflammatory Bowel Disease - Including Crohn's disease and ulcerative colitis
- Thyroid Disorders - Both overactive and underactive thyroid can affect nerves
If you have an autoimmune condition, treating it properly may help
prevent more nerve damage. Some people with autoimmune-related neuropathy
benefit from treatments that calm down the immune system.
Other Medical Conditions
Several other medical conditions can lead to small fiber neuropathy.
These conditions affect your nerves in different ways, but they all can
result in similar symptoms of pain, burning, and numbness.
- Kidney Disease - Waste products that build up when kidneys don't work well can damage nerves
- Liver Disease - Can cause toxic substances to build up and affect nerve function
- HIV/AIDS - The virus itself or some treatments can cause neuropathy
- Vitamin Deficiencies - Especially B12, B1, B6, and folate deficiencies
- Hypothyroidism - Low thyroid hormone levels can slow nerve function
- Fibromyalgia - Often overlaps with small fiber neuropathy
- Amyloidosis - Abnormal protein deposits that can affect nerves
- Vasculitis - Inflammation of blood vessels that can reduce blood flow to nerves
Many of these conditions can be treated, which may help improve your
neuropathy symptoms. Your doctor will test for these conditions as part
of figuring out what's causing your nerve problems.
Medications and Toxins
Some medications and toxic substances can damage small nerve fibers.
The good news is that stopping the harmful substance often prevents more damage and sometimes allows nerves
to heal.
Don't stop taking any prescribed medications without talking to your
doctor first. They can help you weigh the benefits and risks and may be
able to switch you to a different medicine if needed.
- Chemotherapy drugs - Especially platinum-based drugs, taxanes, and vincristine
- HIV medications - Some older HIV drugs are more likely to cause neuropathy
- Antibiotics - Especially fluoroquinolones
- Heart medications - Some drugs used for irregular heartbeat
- Seizure medications - Phenytoin (Dilantin) with long-term use
- Alcohol - Heavy, long-term alcohol use can damage nerves
- Heavy metals - Lead, mercury, arsenic, and thallium exposure
- Industrial chemicals - Some solvents and chemicals used in manufacturing
If your neuropathy is caused by a medication or toxin, stopping the
exposure is the most important step. Your doctor may also recommend
treatments to help your nerves recover and manage any remaining symptoms.
Genetic Factors
Some people inherit genes that make them more likely to develop small
fiber neuropathy. These genetic forms are less common than other causes,
but they're important to recognize because they can affect family members.
Genetic neuropathies often start earlier in life and may progress
differently than other types. If you have family members with similar
symptoms, tell your doctor - this information can help with diagnosis.
- Fabry Disease - A rare genetic disorder affecting how the body processes certain fats
- Hereditary Sensory and Autonomic Neuropathies (HSAN) - A group of inherited conditions affecting sensory nerves
- SCN9A gene mutations - Changes in genes that control sodium channels in nerve cells
- Familial Amyloidosis - Inherited forms of amyloid protein deposits
- Tangier Disease - A rare condition affecting cholesterol metabolism
- Mutations in other ion channel genes - Affecting how nerve cells send signals
If your doctor suspects a genetic cause, they may recommend genetic
testing. This information can help guide treatment and may be important
for family planning decisions. Genetic counseling can help you understand
what the results mean for you and your family.
Written by the SFN Foundation
August 20, 2025
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