Fat emboli are fat droplets within the peripheral circulation – usually in association with traumatic fractures to long bones, such as the femur. The cutaneous manifestations of fat emboli include a transient, nonpalpable petechial eruption that involves the upper torso, oral mucous membranes, conjunctivae, and skin folds of the axillae and neck. The eruption results from occlusion of the dermal capillaries by fat causing increased capillary fragility. It disappears within 24 hours.

The petechiae of fat emboli may signify fat embolism syndrome (FES), which is a life-threatening manifestation. This syndrome involves a triad of the petechial eruption, progressive respiratory failure, and deteriorating mental status. The incidence of FES is fourfold higher in men and in younger patients (aged 10-40 years).

A recent history of significant trauma to lower extremities should prompt a strong clinical suspicion for fat emboli in a patient presenting with a petechial eruption. Nontraumatic causes of fat emboli are rare and include disease processes that involve fat or marrow necrosis (osteomyelitis, acute pancreatitis, panniculitis, bone transplantation). Procedure-related causes of fat emboli include parenteral lipid infusion and intraosseous fluid and drug administration. FES has also been described after orthopedic and plastic surgery procedures (eg, liposuction, fat transplant), or rarely, without known trigger.