Peripheral neuropathy (PN) is damage to or disease affecting nerves, which may impair sensation, movement, gland or organ function, or other aspects of health, depending on the type of nerve affected. Common causes include systemic diseases (such as diabetes or leprosy), vitamin deficiency, medication (e.g., chemotherapy), traumatic injury, radiation therapy, excessive alcohol consumption, immune system disease, Coeliac disease, or viral infection. It can also be genetic (present from birth) or idiopathic (no known cause). In conventional medical usage, the word neuropathy (, "nervous system" and , "disease of") without modifier usually means peripheral neuropathy.