A 55-year-old man is brought to the mortuary 72 hours after death. On examination, the body shows dark discoloration of the skin, particularly over the abdomen and chest. The pathologist notes that the discoloration blanches on pressure in some areas but not in others. Which of the following best explains this finding?

Explanation

## Post-Mortem Discoloration: Livor Mortis vs. Fixed Hypostasis **Key Point:** The critical distinction in this case is whether the discoloration blanches on pressure. ### Timeline of Hypostasis Evolution: 1. **0–8 hours:** Livor mortis appears; blanches on pressure (RBCs intact in dependent vessels, no tissue diffusion) 2. **8–12 hours:** Blanching becomes incomplete as haemoglobin begins to diffuse into surrounding tissues 3. **12+ hours (especially by 72 hours):** Fixed hypostasis develops; does NOT blanch because haemoglobin has diffused into tissue spaces and cells have lysed ### Why Partial Blanching at 72 Hours? At 72 hours post-mortem, the finding of **partial blanching** indicates: - Some areas still have intact RBCs in vessels (blanch) - Other areas show tissue diffusion of haemoglobin (do not blanch) - This mixed pattern is characteristic of the **transition from livor mortis to fixed hypostasis** **Clinical Pearl:** By 72 hours, most of the discoloration should be fixed (non-blanching) due to haemolysis and tissue diffusion. The presence of any blanching suggests either: - Incomplete fixation process, OR - Variable tissue perfusion at time of death ### Forensic Significance: - **Livor mortis** (0–12 hrs): Blanches → indicates death occurred in that position - **Fixed hypostasis** (12+ hrs): Does not blanch → position cannot be reliably determined; body may have been moved post-mortem **High-Yield:** In decomposed bodies, always assess blanching pattern to estimate post-mortem interval and detect body movement.