Hereditary Neuropathy With Liability To Pressure Palsies
Hereditary neuropathy with liability to pressure palsies (HNPP) is a disorder that affects peripheral nerves, causing the nerves to be highly sensitive to pressure. Symptoms usually begin during adolescence or early adulthood but may develop anytime from childhood to late adulthood. Symptoms vary in severity. While some people never realize they have the disorder, others experience prolonged disability. The most common problem sites involve nerves in the wrists, elbows, and knees; however, the fingers, shoulders, hands, feet, and scalp can also be affected. Symptoms associated with HNPP occur in episodes, due to pressure on any single peripheral nerve. Symptoms may include numbness, tingling, and/or loss of muscle function (palsy), pain in the limbs (especially the hands), carpal tunnel syndrome (impairing the ability to use the fingers, hands, and wrists), and foot drop (making it hard or impossible to walk, climb stairs, or drive). Some people experience fatigue, generalized weakness, muscle cramps, pain in the muscles or bones, or lower back pain. An episode of symptoms associated with HNPP can last from several minutes to days or even months. Most people completely recover after an episode, but repeated episodes can cause permanent muscle weakness or loss of sensation.
HNPP is most often caused by the loss of one copy (a deletion) of the PMP22 gene, but it may also be cause by a mutation within this gene. It is inherited in an autosomal dominant manner. The diagnosis is made based on the symptoms present, electrodiagnostic testing, and genetic testing. HNPP is thought to be underdiagnosed, and it may be misdiagnosed as another disorder such as Charcot-Marie Tooth disease.
There is currently no standard medical treatment for HNPP. Management generally involves strategies to avoid or modify positions (such as leaning on the elbows) and activities that cause symptoms, and using splints or pads on the wrists or arms to avoid pressure on the nerves. An ankle-foot orthosis may be needed permanently for those with a residual foot drop. Management of pain may include over-the-counter pain medicines and/or prescription drugs used for peripheral neuropathy. Special work or school accommodations may be necessary. While the long-term outlook (prognosis) regarding quality of life depends on the frequency and severity of episodes and whether pain and disability persist, HNPP does not affect life expectancy.
HNPP is most often caused by the loss of one copy (a deletion) of the PMP22 gene, but it may also be cause by a mutation within this gene. It is inherited in an autosomal dominant manner. The diagnosis is made based on the symptoms present, electrodiagnostic testing, and genetic testing. HNPP is thought to be underdiagnosed, and it may be misdiagnosed as another disorder such as Charcot-Marie Tooth disease.
There is currently no standard medical treatment for HNPP. Management generally involves strategies to avoid or modify positions (such as leaning on the elbows) and activities that cause symptoms, and using splints or pads on the wrists or arms to avoid pressure on the nerves. An ankle-foot orthosis may be needed permanently for those with a residual foot drop. Management of pain may include over-the-counter pain medicines and/or prescription drugs used for peripheral neuropathy. Special work or school accommodations may be necessary. While the long-term outlook (prognosis) regarding quality of life depends on the frequency and severity of episodes and whether pain and disability persist, HNPP does not affect life expectancy.