Neuropathy hereditary with liability to pressure palsies

Neuropathy, Hereditary with Liability to Pressure Palsies (HNPP) is a genetic disorder characterized by recurrent episodes of nerve damage (neuropathy) in response to minimal trauma or pressure on the nerves. This condition is caused by a deletion or mutation in the PMP22 gene, which is crucial for the normal structure and function of the peripheral nerves. HNPP is inherited in an autosomal dominant manner, meaning a single copy of the altered gene in each cell is sufficient to cause the disorder.

Symptoms and Diagnosis

The symptoms of HNPP vary widely among affected individuals but commonly include numbness, tingling, and muscle weakness in the limbs. These symptoms are often triggered by minor pressures such as leaning on elbows, crossing legs, or carrying heavy bags. In some cases, individuals may experience acute episodes of nerve palsy, such as a foot drop or wrist drop, which usually recover over weeks to months.

Diagnosis of HNPP is based on clinical evaluation, family history, and genetic testing to identify mutations in the PMP22 gene. Electrophysiological studies, such as nerve conduction studies, can also support the diagnosis by demonstrating characteristic features of demyelination in affected nerves.

Management and Treatment

There is no cure for HNPP, but the condition can be managed with lifestyle modifications and supportive care. Individuals with HNPP are advised to avoid activities that put pressure on nerves or increase the risk of nerve injury. In cases of acute nerve palsy, physical therapy may be recommended to maintain muscle strength and range of motion until recovery. Pain management, including the use of analgesics or anti-inflammatory medications, may be necessary for some individuals.

Genetic and Molecular Basis

HNPP is most commonly caused by a deletion of one copy of the PMP22 gene on chromosome 17. The PMP22 gene plays a critical role in the development and maintenance of the myelin sheath, a protective covering that surrounds nerve fibers. Without a normal myelin sheath, nerves are more susceptible to damage from compression or trauma. Less commonly, HNPP can result from point mutations in the PMP22 gene that affect the gene's function.

Epidemiology

HNPP is a rare condition, with an estimated prevalence of 1 in 50,000 to 1 in 20,000 individuals worldwide. The disorder affects males and females equally and can present at any age, although symptoms often first appear in adolescence or early adulthood.

See Also

• Peripheral Neuropathy
• Charcot-Marie-Tooth Disease
• Genetic Disorders
• Nerve Conduction Study

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