Hereditary Neuropathy With Liability to Pressure Palsies
An inherited tendency for nerves to be injured by pressure
Quick Facts
- Type: Inherited peripheral nerve disorder
- Cause: Genetic change affecting the PMP22 gene
- Hallmark: Nerve symptoms triggered by minor pressure
- Pattern: Usually recovers, often within weeks
Overview
Hereditary neuropathy with liability to pressure palsies, usually shortened to HNPP, is an inherited condition in which the peripheral nerves are abnormally sensitive to pressure. In most people, leaning on an elbow or crossing the legs causes only brief tingling that quickly resolves. In someone with HNPP, the same everyday pressure can compress a nerve enough to cause numbness, tingling, or weakness that lasts much longer.
The condition is caused by a change in a gene that helps build the protective myelin sheath around nerves, making the nerves fragile at points where they are squeezed. Episodes typically come on after minor compression and usually recover on their own over days to weeks. HNPP is generally mild compared with many other nerve disorders, but recurring episodes can be troublesome.
Symptoms
Symptoms appear suddenly, usually in a single nerve area, after pressure on that nerve.
- Numbness, tingling, or pins-and-needles in a hand, foot, or limb
- Weakness of a specific muscle group, such as a wrist drop or foot drop
- Symptoms that follow a clear trigger, like leaning on an elbow, crossing the legs, or carrying a heavy bag
- Episodes that come and go, often recovering fully over days to weeks
- In some people, a milder background numbness between episodes
Because attacks usually resolve, HNPP is generally not dangerous, but new or persistent weakness should be evaluated to confirm the cause.
Causes
HNPP is a genetic condition, meaning it is caused by a change in a person's DNA and can be passed down in families.
- PMP22 gene change: Most cases result from the loss of one copy of a gene called PMP22, which is needed to make normal myelin, the insulating layer of nerves.
- Fragile nerves: With less of this protein, the myelin is more easily injured where nerves are compressed.
It is inherited in an autosomal dominant pattern, so a parent with HNPP has a chance of passing it to each child. Some people develop the gene change without a clear family history.
Risk Factors
- A parent or close relative with HNPP or unexplained recurrent nerve palsies
- Activities or habits that put pressure on nerves, such as repetitive leaning, crossing the legs, or carrying heavy loads
- Rapid weight loss, which reduces the natural cushioning around nerves
- Surgery or prolonged positioning that compresses a nerve
Diagnosis
Diagnosis combines the typical history of pressure-triggered episodes with nerve testing and genetics.
- Nerve conduction studies: Often show characteristic slowing at common pressure points, even in nerves without symptoms.
- Genetic testing: Can confirm the PMP22 gene change, securing the diagnosis.
- Medical and family history: Recurrent palsies triggered by minor pressure strongly suggest the condition.
- Nerve biopsy: Rarely needed now that genetic testing is available.
Treatment
There is no cure for the genetic change, so management focuses on preventing nerve compression and supporting recovery between episodes.
- Avoiding pressure: Changing habits and using padding to protect vulnerable nerves at the elbows, knees, and wrists.
- Physical and occupational therapy: Helps maintain strength and function and teaches protective techniques.
- Supportive devices: Braces or splints, such as for a foot drop, while a nerve recovers.
- Education: Recognizing triggers and informing surgeons and anesthetists before procedures so positioning can be adjusted.
Most episodes recover on their own, and the overall outlook is generally good.
Prevention
- Avoid leaning on the elbows or crossing the legs for long periods
- Use cushioning at workstations and on hard surfaces
- Take breaks and change position during repetitive tasks
- Tell surgical and anesthetic teams about HNPP so they can pad and position carefully
- Maintain a healthy weight to keep natural nerve cushioning
When to See a Doctor
See a doctor if you have recurring episodes of numbness or weakness triggered by minor pressure, especially if they run in your family. Seek prompt evaluation if weakness:
- Does not recover over the expected days to weeks
- Becomes severe or affects your ability to walk or use a hand
- Occurs with other unexplained symptoms
Confirming the diagnosis helps guide protective measures and informs care before any surgery.
Frequently Asked Questions
What is HNPP?
HNPP, or hereditary neuropathy with liability to pressure palsies, is an inherited condition that makes peripheral nerves unusually fragile to pressure. Minor compression, such as leaning on an elbow, can cause episodes of numbness, tingling, or weakness that usually recover over days to weeks.
What causes HNPP?
It is caused by the loss of one copy of the PMP22 gene, which is needed to make normal myelin, the insulating layer of nerves. With less of this protein, the nerves are easily injured where they are compressed. It is usually inherited from a parent.
Is HNPP dangerous?
It is generally mild. Episodes are triggered by pressure and usually resolve on their own, and the condition does not typically shorten life. However, persistent or severe weakness should be evaluated, and recurrent episodes can be inconvenient.
Can HNPP be cured?
There is no cure for the underlying genetic change, but the condition is manageable. The focus is on protecting nerves from pressure, physical therapy, and supportive devices while episodes recover. Most people do well with these measures.
Should I tell my surgeon I have HNPP?
Yes. Prolonged positioning during surgery can compress nerves, so informing your surgical and anesthetic team allows them to pad and position you carefully. This helps prevent a pressure palsy during or after a procedure.
References
- National Institute of Neurological Disorders and Stroke (NINDS). Peripheral Neuropathy.
- Charcot-Marie-Tooth Association. Related neuropathies.
- MedlinePlus, U.S. National Library of Medicine. Hereditary neuropathy with liability to pressure palsies.
- National Library of Medicine. StatPearls: Hereditary Neuropathy With Liability to Pressure Palsies.