Vaccinia gangrenosa, also known as progressive vaccinia, is a rare but serious complication from the smallpox vaccine. This condition causes the virus to spread from the site of the vaccination and cause tissue destruction, leading to gangrene. While the term "vaccinia gangrenosa" is specific to this complication from the smallpox vaccine, other terms may be used to describe gangrene caused by other factors. These synonyms can include gas gangrene, wet gangrene, and necrotizing fasciitis. Regardless of the cause or the term used to describe it, gangrene is a serious medical condition that requires prompt treatment to prevent the spread of infection and potential loss of limbs or life.