Mononeuritis multiplex: Inflammation of two or more nerves, typically in unrelated parts of the body. Mononeuritis multiplex causes a loss of function in the muscle tissue that is innervated by the affected nerves. For example, sudden loss of the ability to lift the foot normally while walking (foot drop) can be caused by mononeuritis multiplex, when it is accompanied by loss of nerve function elsewhere in the body. There are many causes of mononeuritis multiplex, including diabetes mellitus; infections, such as AIDS, Lyme disease, and leprosy; sarcoidosis; and connective tissue diseases, such as rheumatoid arthritis, systemic lupus erythematosus, vasculitis, Churg-Strauss syndrome, cryoglobulinemia, and Sjogren syndrome. The treatment for mononeuritis multiplex depends on the underlying cause.