An embolism is a sudden interruption of a liquid circulating in the body, blood or lymph, by a foreign body. The fat embolism refers to the migration of fatty masses in the bloodstream. These fatty deposits come from the bone marrow of a long bone fracture, mostly from the shaft (in the middle part of the bone) of the femur. These masses form a clot that will clog an artery, notably the pulmonary artery, responsible for sudden respiratory failure. The fat embolism can also affect other organs like the brain and create a stroke, the kidneys, or the eyes. Fat embolisms can be fatal, but are most often without relapse once symptoms have stabilized.