Fat embolism syndrome (FES) is a rare clinical condition caused by circulating fat emboli leading to a multisystemic dysfunction. The classical clinical triad consists of:
- respiratory distress
- cerebral abnormalities
- petechial haemorrhages
It occurs in ~2.5% (range 0.5-4%) of those with fat embolism, a phenomenon that subclinically occurs in a vast majority of patients (>90%) with bone fractures and during orthopaedic prosthetic procedures.
Symptoms usually develop 1-2 days after the event. Although fat emboli can virtually reach any organ in the body, the results of the embolic shower are most often evident in the lungs, brain, and skin.
Pulmonary dysfunction is present in 75% of patients and is the earliest to be manifested 6. The presence of numerous fat globules in the small pulmonary vessels results in dyspnoea and further hypoxaemia.
Neurological symptoms are seen in 86% of patients 6: ranging from acute confusion to drowsiness, rigidity, convulsions, or coma.
The skin manifestation is characterised by a petechial rash in the chest, axilla, conjunctiva, and neck that appears within 24–36 hours and disappears within a week 6.
Gurd's and Wilson's criteria requires the presence of at least one major and at least four minor criteria:
- petechial rash
- respiratory insufficiency
- cerebral involvement
- retinal changes
- renal signs
- high ESR
- fat macroglobulinemia
Fat particles, from bone marrow after lower extremity fracture, or from vessels and heart after cardiac surgery, are released in blood circulation then embolise to, and occlude, the pulmonary capillaries. Some of the fat globules can pass through the pulmonary capillaries and reach intracranial capillaries. Pathophysiology is thought to be most likely due to both mechanical obstruction as well as a secondary inflammatory response to the released free fatty acids from trapped fat particles within the small vessels. Consumptive thrombocytopenia and anaemia are common complications of fat embolism.
Fat embolism syndrome remains a clinical diagnosis. Imaging may aid to exclude competing differential diagnosis or be suggestive of fat embolism.
- three predominate patterns are observed 1
- filling defects in pulmonary arteries are rarely described in non-fulminant syndromes
May show foci of vasogenic oedema in a random (i.e. embolic) distribution. A "starfield" pattern may be seen on DWI.
History and etymology
The fat embolism syndrome was first described as a clinical entity by E Von Bergmann in 1873 6,7. It is thought to have been clinically described as a post-mortem finding by Zenker in 1862.
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