necrotic

Necrosis is a form of tissue death that occurs when cells in living tissue die due to injury or disease. It involves loss of cell membrane integrity, enzymatic digestion, and inflammation as intracellular contents spill into the extracellular space. Unlike apoptosis, necrosis is typically uncontrolled and irreversible.

Causes include ischemia or hypoxia, physical or chemical toxins, infections, trauma, radiation, and immune reactions. The pattern of necrosis varies by tissue and mechanism. Coagulative necrosis preserves the basic tissue architecture for a time, despite protein denaturation, and is typical of ischemic injury to the heart, kidney, and other solid organs. Liquefactive necrosis results from digestion of tissue by hydrolytic enzymes, producing a liquid mass, as seen in brain infarcts and abscesses. Caseous necrosis combines necrosis with granulomatous inflammation and has a cheese-like appearance, commonly in pulmonary tuberculosis. Fat necrosis, from lipase activity or trauma to fat, yields chalky deposits through saponification. Fibrinoid necrosis involves immune complex–mediated damage to vessel walls, giving a bright pink appearance on histology.

Clinically, necrosis can impair organ function and may predispose to infection or systemic inflammatory response. Management focuses on treating the underlying cause and, when necessary, removing necrotic tissue (debridement) and controlling infection. Necrosis is a histopathological finding and is distinguished from regulated forms of cell death such as apoptosis or necroptosis.