Fat Embolism Syndrome (FES) is a rare but potentially serious complication following trauma, most commonly associated with long bone fractures. It presents with a triad of respiratory distress, neurological symptoms and petechial rash. Although widely recognized, its diagnosis remains challenging due to its variable presentation and overlap with other causes of acute respiratory distress syndrome (ARDS) [8].

Here, we report the case of 31 year old male patient with left tibial shaft fracture having relatively insidious onset of ARDS and difficult to diagnose FES.

31 yrs old man, previously healthy and nonsmoker, admitted to hospital with lower leg long bone fractures (tibia and fibula) after being hit by motorcycle. No chest injuries or other significant injuries were noted.

Vitals on admission: HR: 78/min BP: 124/68mmhg, Spo2 97% RA. A plaster cast was applied and limb was immobilised. On the fourth day post-injury, he developed acute respiratory distress, confusion and tachypnea regardless of limb being immobilized. His oxygen saturation dropped to 76% on room air with no hemodynamic instability. 

ABG and blood investigations sent and oxygen via Venturi FiO2 60% started which improved his saturation (ABG). X-ray chest on admission was Normal but on 5^th day of admission X-ray shows B/L diffuse alveolar involvement (Figure 1).

Blood investigations was normal, with slight increase in ESR. Coagulation study was normal. On 6^th day of admission HRCT Chest was done.

HRCT chest scan revealed multiple air space opacities, ground glass opacities with inter lobular septal thickening including bilateral lung fields. Bilateral     mild     pleural     effusion     with     dependent atelectasis and patches of consolidation including apical segment   of  left  upper  lobe,  post  segment  of  RUL (Figure 2), raising suspicion for FES:

Figure 1: Chest X-ray on admission (Normal) vs. Day 4 (Abnormal with bilateral infiltrates)

Figure 2: HRCT Chest showing bilateral ground-glass opacities and pleural effusion

• ARDS was diagnosed in CT scan without clear cut cause 

• There were no petechial rashes, no tachycardia

• Documented temperature was 98-99 degreeF

• Urine for fat globules was sent and was negative

• Rtpcr on nasopharyngeal swab for SARS cov-2 was sent and was negative

During his stay, his oxygen requirement was static on first 3 days and he was in moderate ARDS. He neither could be weaned off nor needed increased oxygen support to maintain the target saturations. He continued to be tachypnoeic with RR 35-45/min. He was afebrile and heart was normal with sinus rhythm. Patients’ surgery was planned and shifted to operating room with Venturi mask FiO2 60%. CRIF with PFN done under spinal anaesthesia and patient was shifted to general ICU with oxygen via Venturi FiO2 60%. 

In ICU pt underwent dilated fundoscopy which showed retinal fat exudates. Despite no petechial rash, fundoscopy revealed retinal fat emboli, further supporting the diagnosis.

On day 2  of  icu  stay,  pt  was  weaned  to  face mask and on day 3 of ICU stay Patient’s room air saturation was 95-96% with RR 12-16/min and shifted to ward.

Differential Diagnosis of ARDS in this Scenario

In this case, three primary differential diagnoses were considered to explain the development of acute respiratory distress syndrome (ARDS) during hospitalization: post-consolidation pneumonia, COVID pneumonia and fat embolism syndrome (FES).

Post-consolidation pneumonia was a strong consideration given the patient’s shortness of breath, lung consolidation evident on CT imaging, hypoxia and the clinical deterioration occurring by the fourth day of hospitalization. However, several findings argued against this diagnosis. Notably, the absence of classical infectious symptoms such as fever, cough and sputum production, along with unremarkable chest auscultation (no crackles, rales, or bronchial breath sounds), made an infectious etiology less likely. Additionally, laboratory parameters including normal white blood cell count, normal C-Reactive Protein (CRP) and normal procalcitonin levels further diminished the probability of an active infection. Management in this scenario would require ICU admission, provision of ventilatory support, broad-spectrum antibiotics, stabilization of the patient’s condition and only then proceeding to definitive surgical intervention.

COVID pneumonia was also considered because the clinical deterioration occurred on the fourth day of hospitalization, a timeline consistent with COVID-related pulmonary compromise. However, a negative RTPCR test for SARS-CoV-2 argued strongly against this diagnosis. If COVID pneumonia had been confirmed, the management would have included isolation measures, close monitoring of severity markers, ventilatory support, stabilization and, subsequently, definitive surgical care.

Fat embolism syndrome (FES) emerged as another important differential diagnosis, particularly given the history of bone fracture and the presence of tachypnea. High-resolution CT (HRCT) imaging revealed consolidation with atelectasis, findings that can be seen in FES. Nonetheless, certain features made FES less likely: classically, FES presents within 48 hours of injury, whereas this patient’s deterioration occurred on the fourth day of admission. Moreover, the absence of petechiae—a hallmark clinical feature of FES—further weakened this possibility. Management of FES differs in urgency, requiring immediate definitive surgical stabilization of the fracture along with intensive ICU supportive care.

Pathophysiology

Two main theories explain FES:

1. Mechanical Theory-Increased intramedullary pressure forces fat globules into the bloodstream, leading to embolization and pulmonary microvascular occlusion [9]

2. Biochemical Theory-Fat breakdown generates free fatty acids, leading to capillary damage, inflammation and organ dysfunction 

FES typically manifests within 12 to 72 hours post-injury and is characterized by a triad of respiratory insufficiency, petechial rash and neurological dysfunction. The most common manifestation is hypoxia (96% of cases), while neurological symptoms occur in 86% of patients . Petechial rash, seen within 24-36 hours, was absent in our case. Other nonspecific symptoms include fever, thrombocytopenia, jaundice and retinopathy. Severe cases may result in Disseminated Intravascular Coagulation (DIC), right ventricular dysfunction, shock and death.

Diagnostic criteria

Gurd’s Criteria

A diagnosis requires at least one major and four minor criteria.

Schonfeld’s Criteria

A total score ≥5 suggests a high probability of FES.

Lindeque’s Criteria

A diagnosis is made if any one of these criteria is met.

Management

Although systemic corticosteroids may reduce lung inflammation and improve outcomes, their use remains controversial. Heparin has been proposed to stimulate lipase and clear lipids but may exacerbate inflammation [9]. Early stabilization of long bone fractures is crucial in preventing further embolization. A meta-analysis found that early surgical fixation (<24 hours post-injury) reduced FES risk (RR 0.16, 95% CI: 0.08-0.35).

The mainstay of treatment is supportive care, including:

• Oxygen therapy-Supplemental oxygen or mechanical ventilation for hypoxemia

• Hemodynamic support-Ensuring adequate perfusion and preventing hypotension

• Corticosteroids-Controversial, but some studies suggest they may reduce lung inflammation and ARDS progression 

• Early fracture stabilization-Reduces ongoing embolization risk 

Although systemic corticosteroids may reduce lung inflammation and improve outcomes, their use remains controversial. Heparin has been proposed to stimulate lipase and clear lipids but may exacerbate inflammation. Early stabilization of long bone fractures is crucial in preventing further embolization. A meta-analysis found that early surgical fixation (<24 hours post-injury) reduced FES risk (RR 0.16, 95% CI: 0.08-0.35).

Prognosis

• With early recognition and supportive care, mortality is <10%

• Severe cases may develop ARDS, cerebral dysfunction and multi-organ failure, increasing mortality risk

FES remains a clinical diagnosis, with early suspicion and supportive management playing a crucial role in recovery. Prompt fracture fixation and oxygen therapy are key interventions to improve patient outcomes.

1. Gupta, A. and C.S. Reilly. "Fat Embolism." BJA Education, vol. 18, no. 6, 2018, pp. 183–188. doi:10.1016/j.bjae.2018. 04.004.

2. Kwiatt, M.E. and M.J. Seamon. "Fat Embolism Syndrome." International Journal of Critical Illness and Injury Science, vol. 3, no. 1, 2013, pp. 64–68. doi:10.4103/2229-5151. 109426.

3. Mellor, A. and N. Soni. "Fat Embolism." Anaesthesia, vol. 56, no. 2, 2001, pp. 145-154. doi:10.1046/j.1365-2044.2001. 01724.x.

4. Stein, P.D., et al. "Fat Embolism Syndrome." American Journal of the Medical Sciences, vol. 336, no. 6, 2008, pp. 472-477. doi:10.1097/MAJ.0b013e3181805ea1.

5. Bulger, E.M., D.G. Smith and R.V. Maier. "Fat Embolism Syndrome." Critical Care Clinics, vol. 20, no. 3, 2004, pp. 287-303. doi:10.1016/j.ccc.2004.03.011.

6. Shaikh, N. "Emergency Management of Fat Embolism Syndrome." Journal of Emergencies, Trauma and Shock, vol. 2, no. 1, 2009, pp. 29-33. doi:10.4103/0974-2700.44678.

7. Parizel, P.M., et al. "Early Diagnosis of Cerebral Fat Embolism Syndrome by Diffusion-Weighted MRI (Starfield Pattern)." Stroke, vol. 32, no. 12, 2001, pp. 2942-2944. doi:10.1161/hs1201.099784.

8. Husebye, E.E., T. Lyberg and O. Røise. "Bone Marrow Fat in the Circulation: Clinical Entities and Pathophysiological Mechanisms." Injury, vol. 37, Suppl. 4, 2006, pp. S8-S18. doi:10.1016/j.injury.2006.08.042.

9. Lindeque, B.G., H.S. Schoeman and G.F. Dommisse. "Fat Embolism and the Fat Embolism Syndrome: A Double-Blind Therapeutic Study." Journal of Bone and Joint Surgery (British Volume), vol. 69, no. 1, 1987, pp. 128-131. doi:10.1302/0301-620X.69B1.3818704.