Causes
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 it can sometimes slow or stop more nerve damage. If your small fiber neuropathy has been labeled "idiopathic", keep asking your doctor for tests. Diabetes is the most common identifiable cause, but there are 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. Diabetes comes in several forms that can damage nerves, including type 1 and type 2 diabetes, pre-diabetes and insulin resistance, metabolic syndrome, and slower-developing autoimmune diabetes (LADA). Managing blood sugar can help protect nerves.
Diabetes comes in several forms that can damage nerves, including type 1 and type 2 diabetes, pre-diabetes and insulin resistance, metabolic syndrome, and slower-developing autoimmune diabetes (LADA). Managing blood sugar can help protect nerves.
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.
Certain medicines and toxins can harm small nerves, such as some chemotherapy drugs, older HIV medications, certain antibiotics, some heart or seizure drugs, heavy alcohol use, heavy metals, and industrial chemicals. Stopping or switching the offending agent often helps.
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 as this information can help with diagnosis. Learn more about getting a SFN diagnosis.
Rare genetic causes include Fabry disease, hereditary sensory and autonomic neuropathies (HSAN), mutations in ion channel genes like SCN9A, familial amyloidosis, and other inherited metabolic conditions. Genetic testing may be recommended when family history suggests a hereditary cause.
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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