PMP 22 is a 22 kDa glycoprotein expressed in the compact myelin of the peripheral nervous system. In the peripheral nervous system, PMP 22 is produced by myelinating Schwann cells and is coexpressed with the genes for myelin basic protein (MBP) during nerve development and regeneration. Alterations in the level of this protein cause several genetic human diseases. If the protein is duplicated, patients develop Charcot Marie Tooth disease. If one copy of the gene is deleted, they suffer from the inherited tendency to pressure palsies.