This paper described the pathophysiology of suicide deaths from paraquat poisoning which occurred in patients who died in fewer than 24 hours after ingesting paraquat. These deaths were referred to as hyperacute paraquat poisoning deaths. Thrombotic microangiopathy was the predominant pathological finding in all these cases and was evident in the brain, lung, heart, kidneys and in all organs and tissues examined. Of note, diffuse alveolar capillary thrombosis occurred, causing damage to alveolar walls, including those in subpleural locations, resulting in focal visceral pleural rupture leading to pneumothorax and pneumomediastinum in these cases, thus giving rise to yet another mechanism of pneumothorax and pneumomediastinum in paraquat toxicity. Thrombotic microangiopathy is the major pathological mechanism that underlies paraquat poisoning and has not hitherto been reported.