Manganism or manganese poisoning is a toxic condition resulting from chronic exposure to manganese and first identified in 1837 by James Couper. Its symptoms resemble those of idiopathic Parkinson's disease, which it is often misdiagnosed as, although there are particular differences in both the symptoms (nature of tremors, for example), response to drugs such as Levadopa, and affected portion of the basal ganglia. Symptoms are also similar to Lou Gehrig's disease and multiple sclerosis.
Manganism has become an active issue in workplace safety as it has been the subject of numerous product liability lawsuits against manufacturers of arc welding supplies. In these lawsuits, welders have accused the manufacturers of failing to provide adequate warning that their products could cause welding fumes to contain dangerously high manganese concentrations that could lead welders to develop manganism.