Pleiotrophin is used to treat various conditions, disorders, and diseases which involve damage to the peripheral nervous system. Such conditions include traumatic nerve damage, Charcot-Marie-Tooth disease, amyotrophic lateral sclerosis, spinobulbar muscular atrophy, spinal muscular atrophy, diabetic neuropathy, and uremic neuropathy. Pleiotrophin can be provided as a protein or as a gene therapy to a patient in need thereof.