Emboli are objects in the circulatory system which migrate downstream to the flow of blood capable of blocking blood flow. Fat emboli can occur when there is a chance for fat to enter the circulatory system, for example during surgery or trauma. A common scenario is fatty bone marrow entering the circulation after a fracture to a long bone such as the femur or pelvis, or after surgery on such a bone. It can also occur during childbirth. Unlike emboli that arise from thrombi (blood clots), fat emboli are small and multiple, and so have widespread effects. Symptoms usually occur 1-3 days after emolization, and are predominantly: pulmonary (shortness of breath, hypoxemia), neurological (agitation, delirium, or coma), dermatological (petechial rash), and haematological (anaemia, low platelets). The syndrome manifests more frequently in closed fractures of the pelvis or long bones. The petechial rash, which usually resolves in 5-7 days is said to be specific to the syndrome; however, it only occurs in 20-50% of cases.
The risk of fat embolism syndrome is reduced by early immobilization of fractures, especially by early operative correction. Steroid prophylaxis of high risk patients may also reduce the incidence. Treatment is supportive. The mortality rate of fat embolism syndrome is approximately 10%.