Small fiber neuropathy occurs as a result of damage to the small fibers of the peripheral nervous system. These small fibers detect pain, heat, and itching sensations in the skin. They also regulate the autonomic functions of the cardiovascular system and the gastrointestinal tract.
Damage to the peripheral nervous system that affects the small fibers can cause burning pain or tingling sensations that begin at the feet and progress up the legs to the rest of the body.
Small fiber neuropathy may sometimes signal that a person has an underlying health condition, such as diabetes or an autoimmune disease.
Keep reading to learn more about the causes and symptoms of small fiber neuropathy, as well as how doctors diagnose and treat this condition.
Symptoms
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A person experiencing pain in their feet and hands is the most common early symptom of small fiber neuropathy. However, this condition can also reduce the body’s ability to feel pain in a concentrated area and sense temperature.
As the disease progresses, people may notice symptoms in their knees, legs, and arms.
Other symptoms of small fiber neuropathy include:
- a tingling or prickling sensation
- hypersensitivity to touch and temperature changes
- numbness in the feet, legs, or lower stomach
- bladder control issues
- constipation
- sexual dysfunction
- excessive or infrequent sweating
- skin discoloration
- dry eyes and mouth
- extremely low blood pressure that may cause fainting
- rapid or irregular heartbeat
Symptoms of small fiber neuropathy can range from mild to severe. People often experience mild symptoms that may go unnoticed in the early stages. Over time, symptoms typically worsen and progress to other areas of the body.
Treatment
Treatment for small fiber neuropathy varies depending on the underlying cause. People may notice their neuropathy symptoms improve or resolve entirely when they manage or receive treatment for the underlying medical condition.
For individuals who have diabetes or other metabolic disorders, this means managing blood sugar levels, maintaining a moderate body weight, and eating a healthy, balanced diet.
Exercising regularly and quitting smoking can help heal constricted blood vessels that supply vital nutrients to the nerves.
Doctors may prescribe immunosuppressive drugs to treat people who have autoimmune diseases. These medications suppress immune activity in the body and reduce inflammation.
Other treatment options can help reduce pain due to small fiber neuropathy. These can include:
- antidepressants
- antiseizure medication
- lidocaine creams and patches
- narcotics or opioid-based pain medications
Causes
People often develop small fiber neuropathy due to an underlying medical condition, such as diabetes. According to one study, up to 50% of people who have prediabetes or diabetes also develop small fiber neuropathy.
The National Institutes for Health (NIH) notes that mutations in the SCN9A and SCN10A genes can cause small fiber neuropathy. These genes carry instructions for making sodium channels, which cells use to produce and transmit electrical signals.
Examples of medical conditions that can cause small fiber neuropathy includeTrusted Source:
- metabolic and endocrine disorders
- celiac disease
- Sjogren’s syndrome
- primary systemic amyloidosis
- familial amyloidosis
- Fabry disease
- sarcoidosis
- lupus
- fibromyalgia
- HIV
Other causes include:
- vitamin B-12 deficiency
- alcohol use disorder
- exposure to chemotherapy
- physical injuries
- illicit or prescription drug use
A doctor may diagnose a person with idiopathic small fiber neuropathy if they do not identify an underlying cause. In a 2018 studyTrusted Source of 921 people with small fiber neuropathy, researchers found that 53% of the participants had no associated underlying condition.
Diagnosis
Doctors use a wide range of medical tests when diagnosing small fiber neuropathy. They will begin the diagnostic process by reviewing a person’s medical history and performing a physical exam.
A doctor may ask questions about an individual’s family medical history and any current or previous medical conditions that may explain symptoms.
Many medical professionals consider skin biopsies the “gold standard” test for diagnosing small fiber neuropathy. A skin biopsy is a minimally invasive procedure in which a doctor takes several small skin samples for laboratory analysis.
A technician or pathologist will examine the skin samples under a microscope. A doctor may diagnose small fiber neuropathy if the samples have fewer small nerve fibers than healthy skin.
In some cases, a doctor may also perform a nerve conduction test, electromyography, or both. Although doctors cannot conclusively diagnose small fiber neuropathy with these tests, they can use them to rule out other peripheral neuropathies and muscle disorders.
If necessary, doctors can use laboratory tests to check a person’s blood or urine for signs of glucose intolerance, immune system dysfunction, vitamin deficiencies, and liver or kidney problems.
Outlook and progression
Research published in 2021 suggests that small fiber neuropathy is rare, but more people are receiving a diagnosis.
The authors conclude that most people with a diagnosis do not develop major neurological impairments or disability, but many have other conditions alongside, such as diabetes, Sjögren’s syndrome, and lupus.
Some of these conditions, known as comorbidities, can increase the risk of cardiovascular problems. This, in turn, can affect a person’s overall health and life expectancy.
Vs. fibromyalgia
Doctors can find it challenging to distinguish fibromyalgia from small fiber neuropathy. In 2021, some research suggested the following similarities and differences may exist:
| Small fiber neuropathy | Fibromyalgia | |
| Similar symptoms | widespread pain anxiety depression | widespread pain anxiety depression |
| Symptoms potentially specific to each condition | more intense pain stabbing pain burning or prickling sensation areas that are sensitive to touch dry eyes, mouth, or both changed sweating patterns changes in skin color reduced hair or nail growth on feet changes in experience of temperature in parts of the body | headache problems with the jaw |
| Causes | loss or dysfunction of small nerve fibers between skin layers | problems with central pain processing |
| Other conditions that commonly occur alongside | diabetes and other aspects of metabolic disorder exposure to neurotoxins Sjögren’s syndrome sarcoidosis HIV | post-traumatic stress disorder history of sexual abuse inflammatory disease musculoskeletal disease |
Summary
Small fiber neuropathy is a type of peripheral neuropathy that affects the small nerve fibers in the skin.
This condition usually causes an unpleasant tingling sensation or burning pain in the feet. However, people who have small fiber neuropathy may have reduced sensitivity to heat and certain types of pain.
Although the symptoms of small fiber neuropathy usually begin in a person’s feet, they can also affect their legs, hands, arms, and torso.
People can develop small fiber neuropathy due to nerve damage from another underlying medical condition, such as diabetes, an autoimmune disease, or an injury.
Treatments depend on the underlying cause. In most cases, managing the underlying medical condition can relieve the symptoms of small fiber neuropathy.
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