The precise diagnosis is elusive as there is no specific confirmatory test. The diagnosis is based on a constellation of clinical and laboratory findings (respiratory insufficiency, altered mentation, petechial rash, pyrexia, tachycardia, thrombocytopenia after long bone fracture) and exclusion of other potential diagnoses. Patients 10 - 40 years old are most often affected. Children younger than 10 have a lower fat content in their bones and older adults often do not sustain the major long bone fractures necessary to cause fat embolism.
Treatment is supportive care.
Source
Akhtar, S. "Fat Embolism" Anesthesiology Clin. 2009.