HNPP is caused by a deletion of the peripheral myelin protein 22-kDa (PMP22, OMIM number 601097) gene on chromosome 17p11.2, which encodes an intrinsic, tetraspan membrane glycoprotein that is expressed mainly in Schwann cells and represents an important, although minor, component of the compact myelin of the peripheral nerves [4]. The gene discussed is PMP22; the disease is hereditary neuropathy with liability to pressure palsies.