Bone marrow fat in the circulation: clinical entities and pathophysiological mechanisms

Fat embolism (FE) and fat embolism syndrome (FES) are controversial topics, particularly regarding their clinical relevance and their independency as a clinical syndrome. FE describes the presence of fat globules within the microcirculation. FES on the other hand, is a clinical syndrome characterized by the presence of FE with the manifestation of an identifiable clinical pattern of signs and symptoms. Both experimental and clinical studies have demonstrated the occurrence and the possible harmful effects of FE. For instance, FE involving the lungs can result in adult respiratory distress syndrome (ARDS). The effects of FE are certainly mechanical, leading to capillary congestion, but are also highly likely to be of a proinflammatory and prothrombotic nature. The demarcation of FES against ARDS is mainly demonstrated by the single organ involvement of ARDS, exclusively influencing the lungs, whereas FES has a multiorgan effect with pulmonary, skin and, neurological manifestations. This article is a review of the pathophysiological mechanisms of FE and the clinical occurrence and influence of FE and FES.