Fat embolisms are globules of fat that enter the circulatory system through veins or arteries. The body is usually able to clear fat embolisms before they cause significant damage. However, in rare cases, they cause obstructions that can lead to inflammation, organ dysfunction, and even death. This is known as fat embolism syndrome (FES).

FES is more common in people who have sustained a long bone fracture involving the thighbone, shinbone, calf bone, or pelvis. Fat embolisms are very common following long bone trauma, but only about 1–11% of people go on to experience FES.

FES is more common in males than females, and the risk of developing FES after orthopedic trauma is highest in those aged 10–40 years.

Keep reading to learn more about the causes, symptoms, diagnosis, and treatment of FES.

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The exact cause of FES is still unknown. However, researchers have proposed two main theories: the mechanical obstruction theory and the biochemical theory.

FES most commonly occurs after a fracture to one of the long bones in the body. The long bones contain more fatty bone marrow than smaller bones. When a bone breaks, fat cells within the bone marrow can seep out and enter the bloodstream. These cells clump together to form globules, or emboli.

The mechanical theory suggests that these emboli then circulate the body and obstruct blood vessels in the lungs and elsewhere.

The biochemical theory suggests that the body manufactures chemicals to combat fat emboli, which turn into toxic free fatty acids and glycerol. It is these substances that damage cells and organs, according to this theory.

Although recent bone fractures account for most cases of FES, people have reported other, rarer causes. These include:

Learn more about fat embolisms here.

General symptoms of FES include:

There are three main symptoms of FES, which usually occur 12–72 hours after the initial trauma or during surgical procedures. They involve the lungs, brain, and skin.

Difficulty breathing

The first symptom often involves difficulty with breathing, such as shortness of breath or rapid breathing.

Blood tests might show low levels of oxygen in the blood.

Neurological symptoms

Neurological, or brain-related, symptoms can also occur. These may include:


The third of the primary symptoms, which may appear after the first two, is a petechial rash, which presents as tiny red, purple, or brown spots on the skin. The rash is most likely to occur in these places:

  • the inside of the eyelids
  • in the mouth
  • in the skinfolds of the neck, chest, and armpits

Severe, sudden symptoms

Severe cases of FES with a sudden onset can result in:

FES is difficult to diagnose, primarily because diagnostic scans do not show anything unusual. Doctors can perform a physical examination and blood tests, as well as considering a person’s medical history and any recent bone injuries.

There is no universally agreed system for diagnosing FES. Alongside tests and scans, some doctors use Gurd’s criteria to help with diagnosis. They will diagnose FES if a person has at least one of the major criteria and at least four of the minor criteria.

Gurd’s major criteria include:

  • petechial rash
  • respiratory distress
  • brain involvement

Gurd’s minor criteria include:

Other doctors might use the Schoenfeld criteria, which allocate a different number of points to each possible symptom, to help diagnose FES. The doctor will add up points based on the person’s symptoms to get a score.

According to a 2016 paper in the journal Current Trauma Reports, FES has no specific treatment and requires supportive care. A person with FES is likely to receive treatment in an intensive care unit (ICU) and might receive extra oxygen or mechanical ventilation to support their breathing. In addition, they might receive intravenous drugs to maintain blood volume.

If there are signs to suggest that FES has affected the brain, doctors will perform frequent neurological exams and monitor pressure within the skull. To reduce discomfort, a person will receive an anesthetic.

No specific drugs are suitable for the treatment of FES. However, in people with compromised lung function, corticosteroids may help reduce inflammation, hemorrhage, and swelling, although there is no robust evidence to support their use.

Learn about bone fracture repair here.

Most people with FES will recover. The severity and duration of FES vary from person to person and depend on factors such as:

  • a person’s age
  • their general health
  • underlying health conditions that affect the body’s resilience

FES is often only part of a bigger picture of injuries and illness, so recovery times vary widely. Some people experience ongoing respiratory problems and lasting neurological changes.

According to a recent report, recent studies have established a mortality rate of 7–10% for people with FES.

It is important to remember that these figures are estimates and are based on the results of previous studies or treatments. A person can talk with a healthcare professional about how their condition is likely to affect them.

Several factors can increase the risk of FES developing. These include:

  • young age
  • closed fractures that do not break the skin
  • multiple fractures
  • delayed treatment of a bone fracture

The risk of developing FES increases the longer a fractured bone goes without treatment.

The proper and prompt immobilization of a bone following a fracture creates less opportunity for fatty cells to seep into the bloodstream. If a person suspects that they have fractured a long bone, they should limit their movement and seek medical attention immediately.

The best way to avoid FES is to take steps to prevent fractures from happening in the first place.

Regular, low impact exercise, such as yoga and swimming, can help maintain strong muscles while improving coordination and balance, which can help prevent slips and falls.

People with osteoporosis have a higher risk of breaking bones and should follow medical advice on how to prevent injuries. Doctors may advise:

  • improving muscle strength
  • practicing balance exercises daily
  • working with an eye doctor to maximize vision health

FES is a serious consequence of having fat emboli in the bloodstream. Long bone breaks can trigger fat emboli to enter the circulatory system.

Fat emboli can cause obstructions that lead to multi-organ dysfunction, including respiratory and neurological problems. In general, the sooner a person seeks treatment, the better their outlook.

Although treatment options may be limited, most people recover without lasting consequences.