CD61 and fibrinogen immunohistochemical study to improve the post-mortem diagnosis in a fat embolism syndrome clinically demonstrated by transesophageal echocardiography

Fat embolization following major trauma is reported to be a quite common event, while the clinical fat embolism syndrome (FES) seems to be a much rarer event. Fat embolism occurs in 2 up to 23% of patients with isolated femoral shaft fractures. This complication appears to be related not only to the fracture, but also to the timing of stabilization. Sometimes it may be impossible to perform histochemical reactions on frozen sections to detect fat emboli thus confirming diagnosis or suspicion of FES. The finding of fibrinogen and platelets around the apparently empty spaces in the blood vessels has been proposed as an evidence for vital reaction due to either a vital cellular reaction or a flotation mechanism, thus supporting an intravital fat embolism. We report a fatal case due to fat embolism syndrome in a young man hospitalized for a right femoral neck fracture, treated with orthopaedic surgery and subjected to an intra-surgery transesophageal echocardiography that revealed embolization of numerous highly echogenic bodies. Four hours after the onset of clinical symptoms the man died from respiratory failure. The autopsy confirmed the clinical diagnosis of fat embolism syndrome. The histological examination revealed a large amount of fat globules in cerebral and pulmonary arteries and in glomerular capillaries, as well as fibrin and platelet deposition confirmed by the positive results by Sudan III staining for lipids and immunohistochemistry with anti-CD61 and anti-fibrinogen antibodies. The quantitative classification of fat embolism was grade 3 of Sevitt's classification or grade 4 of Fineschi's quantification, according to the current quantitative microscopic methods used for grading fat embolism in pulmonary tissue.