Intimomedial mucoid arterial degeneration, a rare arterial disorder of forensic significance

The body of a 43-year-old African woman with a history of aortic aneurysm and hypertension was forensically investigated after her sudden death. The cause of death was related to a cardiac tamponade due to a ruptured aneurysm of the ascending aorta. Post-mortem gross examination showed an abnormal whitish discoloration of the intima with fibrous thickening of the aortic wall. Several arteries (left main and circumflex coronaries, carotid, renal and iliac arteries) showed similar features. Upon histological examination, the aortic aneurysm as well as the other arteries sampled showed mucoid degeneration, excess mucopolysaccharides and pools of mucin inside the intima and the media associated with collagen and elastic fiber destruction and loss of smooth muscle cells. This pattern strongly suggested the diagnosis of intimomedial mucoid degeneration (IMMD), a rare arterial disorder consisting of a progressive deposition of mucin into the intima and media, with a strong prevalence in middle-aged black African females with high blood pressure. In addition to the typical features of IMMD, histological examination of the ascending aorta showed a thickening of the adventita with sparse mixed inflammatory infiltrates and fibrosis, suggesting an additional chronic infectious aortitis. No infectious agent was detected. The body of literature on IMMD is reviewed and the origin of death is discussed in this case report.