Hereditary neuropathy with liability to pressure palsy

Myelinated neuron

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Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) is a genetic disorder that affects the peripheral nerves. It is characterized by recurrent episodes of nerve compression that lead to numbness, weakness, and sometimes pain in the affected areas. HNPP is caused by a mutation in the PMP22 gene, which plays a crucial role in the structure and function of the peripheral nerves.

Causes and Genetics

HNPP is an inherited condition that follows an autosomal dominant pattern. This means that a mutation in just one of the two copies of the PMP22 gene can cause the disorder. The PMP22 gene is located on chromosome 17 and is involved in the production of a protein that is essential for the myelin sheath, a protective covering that surrounds nerve fibers. In HNPP, there is typically a deletion of one copy of the PMP22 gene, leading to reduced levels of PMP22 protein. This reduction disrupts the normal function of the peripheral nerves, making them more susceptible to pressure and compression.

Symptoms

The symptoms of HNPP vary widely among individuals but commonly include:

• Temporary numbness, tingling, or loss of muscle function in the affected area
• Episodes of muscle weakness or paralysis that can last from minutes to several months
• Sensory loss in the affected limbs
• Muscle wasting in severe cases

Symptoms are often triggered by minor traumas or pressure on the nerves, such as crossing one's legs, leaning on an elbow, or wearing tight-fitting clothing.

Diagnosis

Diagnosis of HNPP involves a combination of clinical evaluation, family history, and genetic testing. Electromyography (EMG) and nerve conduction studies can help assess the extent of nerve damage and identify characteristic patterns associated with the disorder. Genetic testing is used to confirm the diagnosis by detecting the deletion or mutation in the PMP22 gene.

Treatment and Management

There is no cure for HNPP, but the condition can be managed with lifestyle adjustments and supportive care. Treatment strategies focus on avoiding activities that can trigger symptoms, using protective padding to prevent nerve compression, and physical therapy to strengthen affected muscles and maintain mobility. In some cases, pain management may be necessary to address discomfort associated with nerve damage.

Prognosis

The prognosis for individuals with HNPP is generally good, as the condition tends to be slowly progressive and does not typically affect life expectancy. However, the severity of symptoms and the impact on quality of life can vary. With appropriate management, most people with HNPP can lead active, normal lives.

See Also

• Peripheral Neuropathy
• Charcot-Marie-Tooth Disease
• Genetic Disorders
• Nerve Compression Syndrome