neurologic disorders
Hereditary Motor Neuropathy With Liability to Pressure Palsies (HNPP)
Introduction
In hereditary motor neuropathy with liability to pressure palsies (HNPP), nerves become increasingly sensitive to pressure and stretch. (See also Overview of Peripheral Nervous System Disorders .) In HNPP, peripheral nerves lose their myelin sheath and do not conduct nerve impulses normally. Inheritance is usually autosomal dominant. In 80%, the cause is loss of one copy of peripheral myelin protein-22 gene (PMP22), located on the short arm of chromosome 17. Two copies of the gene are needed for normal function. Incidence of HNPP is estimated to be 2 to 5/100,000. 