Mercury poisoning (also known as mercurialism, hyrargyria, Hunter-Russell syndrome, or acrodynia when affecting children) is a disease caused by exposure to mercury or its toxic compounds. Mercury is a cumulative heavy metal poison which occurs in its elemental form, inorganically as salts, or organically as organomercury compounds; the three groups vary in effects due to differences in their absorption and metabolism, among other factors. However, with sufficient exposure all mercury-based toxic compounds damage the central nervous system and other organs or organ systems such as the liver or gastrointestinal tract.