A common observation in blunt traumatic injuries of the face and body that have resulted in large bruises or hematomas (blood collections) is that soft tissue or contour depressions may appear many months later. This is confusing to patients as they do not know why it occurs since they did not have a laceration or obvious deep tissue injury. What has happened is that the blunt injury has caused fat underneath the skin to atrophy or wither away. But how did a ‘big bruise’ cause fat loss? One mechanism is that the trauma has damaged fat cells by compression. Some fat cells may have been crushed or broken apart by the external force, causing permanent loss of volume. This certainly is one injury mechanism but it probably not the only one. When large bruises develop that are associated with a blunt traumatic injury, the released red blood cells are eventually broken down as part of the bruise clearing process. When red blood cells are broken or are being broken down, the hemoglobin they contain can release their heme prosthetic groups. As the heme decomposes, the non-protein bound heme can become highly cytotoxic due to the iron (Fe+) atom contained within its porphyrin ring. The iron’s ability to donate and accept eIectrons enables it to convert hydrogen peroxide into free radicals. Free radicals are well known to cause damage to cellular structures of which adipocytes (fat cells) would be very susceptible. Localized ‘iron toxicity’ may add to the development of subcutaneous fat atrophy in traumatic injuries.
Dr. Barry Eppley