Finally, hereditary neuropathy with liability to pressure palsies (HNPP), mostly due to peripheral myelin protein 22 (PMP22) deletion, has a pathognomonic pattern of nerve enlargement at entrapment sites (e.g., carpal tunnel, cubital tunnel, fibular tunnel, and supinator loge) with normal nerve segment in between. The gene discussed is PMP22; the disease is hereditary neuropathy with liability to pressure palsies.