Fat Embolism Syndrome (FES)

Fat embolism syndrome (FES) is a collection of symptoms and complications that result from the presence of a fat emboli in the blood. FES most often develops as a result of a long bone fracture, such as a fracture of your femur (leg) bone. However, FES can happen after any bone fracture or even after an injury that may not actually result in a fracture, such as a fall or a hard “bump” into something.

While rare, FES may develop quickly, and the consequences may be serious and life threatening. It is important to know the symptoms of FES to look out for following a fall, fracture, or trauma.

Important FES Facts to Remember

  1. It is rare, but should not be overlooked following a fracture, fall, or other trauma.
  2. Results when fat particles enter the blood circulation, causing decreased blood flow into the lungs and decreased oxygen to the heart and/or brain.
  3. Usually follows long bone/pelvic fractures or trauma; very rarely has occurred after orthopedic surgery.
  4. Should be considered if the person develops shortness of breath or neurological symptoms (abnormal sleepiness or change in behavior).
  5. Symptoms due to fat embolism may develop quickly and become life threatening in just a few hours.

Please keep a copy of the emergency card, or the emergency information on the PPMD mobile app close at hand. Don’t be afraid to talk and keep talking until someone listens!

Why does FES develop?

People with Duchenne are at a higher risk for FES. Like skeletal muscles in Duchenne, the hollow cavity inside bone (called the medullary cavity) is replaced with fat. It is thought that when bone is broken or injured, tiny pieces of fat (from inside the bone) are dislodged and released into the bloodstream. These tiny pieces of fat are known as “fat emboli.” Fat emboli can travel to the lungs. If a fat embolism lodges in the pulmonary (lung) blood vessels, FES develops.This is similar to a pulmonary embolism, which happens when a blood clot from the leg travels into the heart and then the lungs.

Additionally, people with Duchenne have weak bones (osteoporosis), especially if they are on steroids.  This puts them at even higher risk for bone fractures and, consequently, FES.

When to suspect FES

The symptoms of FES can be very nonspecific, making them easily missed or attributed to something else (such as pneumonia or another illness). It is important you be aware of these symptoms and keep emergency information on hand to show emergency department staff if FES is suspected.

Some common symptoms of FES include being sleepier than usual, having unusual changes in behavior, and being short of breath, which quickly develops into difficulty breathing. A person with FES may become more confused, disoriented, agitated and have progressive trouble breathing. If you or someone you know falls, is dropped, or bumped and shows any of these symptoms, go immediately to the emergency room –  this is a life threatening emergency.

Presenting Symptoms

A combination of two major and one minor symptom or one major and four minor symptoms can be used to diagnose FES:

Major Symptoms

  • Shortness of breath (difficulty breathing)
  • Neurologic changes (confusion, headache, coma, seizures)
  • Petechial rash (small dotted rash that develops 24-36 hours after the trauma, usually seen in the sclera of the eyes, under the arms, and/or chest)

Minor Symptoms

  • Tachycardia (fast heart rate, over 140s)
  • Fever
  • Retinal changes (hemorrhages or fat globules upon exam)
  • Jaundice (yellowing of skin or eyes)
  • Decreased platelet counts
  • Decreased red blood cell counts
  • Elevated ESR (blood marker for inflammation)
  • Fat macroglobulinemia (fat particles in the blood)

Pneumonia and heart failure can often cause some of these same symptoms (sleepiness, shortness of breath) to develop and may confuse the emergency staff, but symptoms with those two underlying disorders generally develop slowly.

Emergency Care Management

Go immediately to the Emergency Room if symptoms of shortness of breath or neurologic changes (confusion, disorientation, “not acting like themselves”) occur after a fall or trauma. Some emergency clinicians may not be aware or think about FES initially. It is important to notify the staff that FES is a possibility in Duchenne, requiring close medical examination and monitoring. Always notify your neuromuscular specialist that you are in the emergency room or admitted to the hospital; do not depend on the emergency staff to call them.

Early oxygen saturation is important, and should be suggested if it is not initiated quickly. 80% of FES cases resolve on their own. Emergency department care will be supportive and address the symptoms happening. You should try and minimize physical movement while you are being evaluated for FES to prevent more fat emboli from being dislodged.

If the emergency department doctors decide to admit you to the hospital for monitoring of FES, you should be admitted to an Intensive Care Unit (ICU). A regular hospital inpatient floor may not have the ability to monitor you closely enough and act quickly if symptoms progress.

If your oxygen saturations are low and you require supplemental oxygen, be sure the clinicians use caution. Oxygen use in Duchenne requires close monitoring (i.e. CO2 levels) as it can precipitate respiratory failure. The safest way to give deliver oxygen is through non-invasive ventilation, such as a BiPAP machine. Do not hesitate to agree to have your child intubated if necessary for breathing support.

If you need “back up” when dealing with an emergency situation such as FES, call your neuromuscular providers. You can also call PPMD and we will do whatever we can to help.

If it turns out not to be Fat Embolism Syndrome, that’s ok. It’s much better to suspect fat embolism and find pneumonia, for example, than the other way around. Please keep a copy of the emergency card, or the emergency information on the PPMD mobile app close at hand. Don’t be afraid to be wrong and talk until someone listens!

Studies or Tests to Consider

  • Ophthamalogic exam (eye exam) may detect fat globules in the retina and can be diagnostic of FES
  • Arterial blood gas (checks oxygen in the arterial blood)
  • CBC with diff (checks red blood cells and platelets)
  • Cytological evaluation of urine, blood, sputum for fat
  • Check ESR
  • Chest X-ray (check for infiltrates; may develop over time, may need to repeat)
  • CT scan (to rule out other reasons for symptoms)
  • Brain MRI (check for fat emboli)
  • Bronchoscopy may detect fat globules in the alveolar capillaries and alveoli


When you are in your wheelchair (or are riding on anything with wheels), wear your seat belt!

What Causes FES?

The exact cause of FES is not known, but there are two theories about the development of FES, and why we might see fat globules in different areas of the body, especially the lungs, brain, and heart.

Mechanical Theory

When a bone breaks, droplets of fat are released into the venous circulation ( blood without oxygen going back to the heart then to the lungs to get oxygen). In the heart, the fat globules may travel through openings that pass the fat from the venous circulation to the arterial circulation (or oxygenated blood going from the heart back to the brain and body). In the brain, these fat micro globules produce irritation and inflammation in the walls of the small vessels, or capillaries. The inflammation causes chemical changes that may cause platelets to clump, resulting in decreased circulation to the areas of the brain fed by those capillaries. This decreased circulation causes the symptoms of FES that we see.

Openings in the heart that can allow fat to pass from the venous to the arterial circulation may be a patent foramen ovale or an atrial septal defect. A patent foramen ovale is an opening between the right and left side of the heart that is normal before birth and should close during infancy. An atrial septal defect  is an opening between the two atria (top chambers of the heart) or (less likely) a ventricular septal defect (an opening in the two bottom chambers of the heart).

A patent foramen ovale can be very small and can be missed, but it is diagnosed by a “bubble study” (before an echocardiogram, saline with bubbles is delivered via IV; as it moves to the heart, it is watched via echo; if there is an opening, the bubbles will float through the opening).

Biochemical Theory

With a trauma (such as a bone break), chemical changes in the body may cause a release of free fatty acids in any area of the body (lungs, brain, heart). Further chemical changes that follow the release of fatty acids cause the fatty acids to clump in the capillaries of those areas of the body. This results in decreased circulation to the area fed by those capillaries and the symptoms of FES that we see. In addition, when fat is released from a mechanical injury, that fat is broken down into fatty acids. These fatty acids can circulate to other organs, causing multi organ dysfunction. T2 weighted MRI has been helpful in evaluating the presence of fat emboli/micro globules in the brain.

Additional Resources

Webinar: FES Following Mild Trauma in Duchenne

Presentation: A discussion of FES was presented by Dr. Susan Apkon at the 2017 PPMD Connect Conference


Shaikh, N. (2009). Emergency management of fat embolism syndrome. Journal of emergencies, trauma, and shock, 2(1), 29.

Kwiatt, M. E., & Seamon, M. J. (2013). Fat embolism syndrome. International journal of critical illness and injury science, 3(1), 64.