|HNPP-Hereditary neuropathy with liability to pressure palsy·Autosomal dominant trait with total penetrance but variable expression.· Deletion of the PMP-22 gene on chromosome 17.
· Histopathology studies-tomaculous “sausage like” neuropathy. Focal thickening of myelin sheaths, with apparent compression and flattening of axons at such sites. May have extensive demyelination with re-myelination and onion bulb formation.
· Clinical presentation-single or multiple nerve involvement. May occur after mild compression or traction. Symptoms may reduce, but neurologic abnormalities may persist.
· Median, ulnar, radial, peroneal neuropathy common. NCV changes may occur in clinically unaffected nerves.