Fat Embolism, Fat Embolism Syndrome and the Autopsy

Abstract

Fat embolism is common following trauma and is a common autopsy finding in these cases. It may also be seen in non-traumatic cases and is seen in children as well as adults. In comparison fat embolism syndrome (FES) only occurs in a small number of trauma and non-trauma cases. Clinical diagnosis is based on characteristic clinical and laboratory findings. Fat embolism exerts its effect by mechanical blockage of vessels and/or by biochemical means including breakdown of fat to free fatty acids causing an inflammatory response. Fat embolism can be identified at autopsy on microscopy of the lungs using fat stains conducted on frozen tissue, including on formalin fixed but not processed tissue. With FES fat emboli can be seen in other organs including the brain, kidney and myocardium. Fat can also be identified with post-fixation staining, typically with osmium tetroxide. Scoring systems have been developed to try and determine the severity of fat embolism in lung tissue. Fat embolism is also common following resuscitation. When no resuscitation has taken place, the presence of fat on lung histology has been used as proof of vitality. Diagnosis of fat embolism syndrome at autopsy requires analysis of the history, clinical and laboratory findings along with autopsy investigations to determine its relevance, but is an important diagnosis to make which is not always identified clinically. This paper reviews the history, clinical and laboratory findings and diagnosis of fat embolism and fat embolism syndrome at autopsy.

Keywords: Autopsy; Embolism; Fat; Forensic pathology; Microscopy; Syndrome.

Image 1:

Petechial rash on the torso in fat embolism syndrome.

Image 2:

Lung with fat emboli in distended vessels (H&E, x100).

Image 3:

Lung with fat emboli (Oil red O, x100).

Image 4:

Lung with fat emboli (Osmium tetroxide, x100).

Image 5:

Brain showing fat embolism with prominent petechiae in white matter

Image 6:

Cerebral fat embolism (H&E, x100).

Image 7:

Fat embolism in the brain (Oil red O, x100).

Image 8:

Renal fat embolism (H&E, x200).

Image 9:

Renal fat embolism (Osmium tetroxide, x200).

Image 10:

Fat necrosis in the arm.

Image 11:

Fat necrosis in the leg.

Image 12:

Acute hemorrhage with chronic inflammation (H&E, x200).

Image 13:

Hemosiderin macrophages in damaged fat tissue (Perls’ stain, x200).