Hereditary neuropathy with liability to pressure palsies

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Hereditary neuropathy with liability to pressure palsies is a disorder that affects peripheral nerves. These nerves connect the brain and spinal cord to muscles and sensory cells that detect touch, pain, and temperature. In people with this disorder, the peripheral nerves are unusually sensitive to pressure, such as the pressure that occurs when carrying heavy grocery bags, leaning on an elbow, or sitting without changing position, particularly with crossed legs. These activities would not normally cause sensation problems in people without the disorder.

Hereditary neuropathy with liability to pressure palsies is characterized by recurrent episodes of numbness, tingling, and loss of muscle function (palsy) in the region associated with the affected nerve, usually an arm, hand, leg, or foot. An episode can last from several minutes to several months, but recovery is usually complete. Repeated incidents, however, can cause permanent muscle weakness or loss of sensation. This disorder is also associated with pain in the limbs, especially the hands.

A pressure palsy episode results from pressure on a single nerve, and any peripheral nerve can be affected. Although episodes often recur, they can affect different nerves. The most common problem sites involve nerves in the wrists, elbows, and knees. The fingers, shoulders, hands, feet, and scalp can also be affected. Many people with this disorder experience carpal tunnel syndrome, which occurs when a nerve in the wrist (the median nerve) is involved. Carpal tunnel syndrome is characterized by numbness, tingling, and weakness in the hand and fingers. An episode in the hand may affect fine motor activities such as writing, opening jars, and fastening buttons. An episode of nerve compression in the knee can lead to a condition called foot drop, which makes walking, climbing stairs, or driving difficult or impossible.

The symptoms of hereditary neuropathy with liability to pressure palsies usually begin during adolescence or early adulthood but may develop anytime from childhood to late adulthood. Symptoms vary in severity; many people never realize they have the disorder, while some people experience prolonged disability. Hereditary neuropathy with liability to pressure palsies does not affect life expectancy.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Hereditary neuropathy with liability to pressure palsies is most commonly caused by the deletion of one copy of the PMP22 gene. This loss reduces the amount of PMP22 protein produced. Other PMP22 gene mutations that lead to a reduction of PMP22 protein can also cause the condition.

The PMP22 protein is a component of myelin, a protective substance that covers nerves and promotes the efficient transmission of nerve impulses. Studies suggest that the PMP22 protein is particularly important in protecting nerves from physical pressure, helping them restore their structure after compression. Compression can interrupt nerve signaling, leading to the sensation commonly referred to as a limb "falling asleep." The ability of nerves to recover from normal, day-to-day pressure, for example when sitting for long periods, keeps the limbs from constantly losing sensation.

The consequences of PMP22 gene mutations are not clearly understood. A shortage of PMP22 protein appears to make nerves less able to recover from compression, which impairs the transmission of nerve impulses, causing the signs and symptoms of hereditary neuropathy with liability to pressure palsies.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Hereditary neuropathy with liability to pressure palsies is estimated to occur in 2 to 5 per 100,000 individuals.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Decreased motor nerve conduction velocity · Very frequent (99-80%)

A type of decreased nerve conduction velocity that affects the motor neuron.

Peripheral neuropathy · Very frequent (99-80%)

Peripheral neuropathy is a general term for any disorder of the peripheral nervous system. The main clinical features used to classify peripheral neuropathy are distribution, type (mainly demyelinating versus mainly axonal), duration, and course.

Muscle weakness · Frequent (79-30%)

Reduced strength of muscles.

Paresthesia · Frequent (79-30%)

Abnormal sensations such as tingling, pricking, or numbness of the skin with no apparent physical cause.

Scoliosis · Frequent (79-30%)

The presence of an abnormal lateral curvature of the spine.

Decreased/absent ankle reflexes · Frequent (79-30%)

Sensorimotor neuropathy · Frequent (79-30%)

Distal amyotrophy · Occasional (29-5%)

Muscular atrophy affecting muscles in the distal portions of the extremities.

Other findings in the same source

From: Orphanet

Additional reported features include Exercise-induced myalgia (Occasional (29-5%)); Hyporeflexia (Occasional (29-5%)); Muscle spasm (Occasional (29-5%)); Pes cavus (Occasional (29-5%)); Sensorineural hearing impairment (Occasional (29-5%)); Vocal cord paralysis (Occasional (29-5%)); Abnormality of the voice (Occasional (29-5%)); Cranial nerve paralysis (Occasional (29-5%)); Respiratory insufficiency (Occasional (29-5%)); Scapuloperoneal weakness (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Hereditary neuropathy with liability to pressure palsies is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Hereditary neuropathy with liability to pressure palsies. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.