“Inflammation of prolonged duration (weeks to years) in which continuing inflammation, tissue injury, and healing, often by fibrosis proceed simultaneously”.
Characterized by:
- Infiltration with mononuclear cells, including macrophages, lymphocytes and plasma cells (these three cells are chronic inflammatory cells).
- Tissue destruction largely induced by products of the inflammatory cells.
- Repair, involving new vessel proliferation (angiogenesis) and fibrosis.
Chronic inflammation is a process in which tissue destruction and repair processes go side by side.
![](https://promedscape.com/wp-content/uploads/2023/07/chronic-inflammatory-cells-1024x1024.jpeg)
Acute inflammation may progress to chronic inflammation; by?
- Persistence of infectious agent.
e.g.
–Peptic ulcer of duodenum initially shows acute inflammation.
-Recurrent bouts of duodenal epithelial injury interrupt this process, resulting in a lesion characterized by both acute and chronic inflammation.
![](https://promedscape.com/wp-content/uploads/2023/07/chronic-infl4.webp)
![](https://promedscape.com/wp-content/uploads/2023/07/chronic-infl-3.jpg)
Examples:
Bacterial:
- Tuberculosis (mycobacterium tuberculosis).
- Leprosy (M.Leprae)
- Syphilitic gumma (T.pallidum)
- Cat-scratch disease (gram-negative bacillus)
Fungal:
- Histoplasma capsulatum
- Blastomycosis
- Cryptococcus neoformans
- Coccidioides immitis
Parasitic:
- Schistosomiasis (Schistosoma mansoni, S.haemotobium, S.japonicum)
Inorganic metals or dusts:
- Silicosis
Foreign body:
- Suture, breast prosthesis, vascular graft
Unknown:
- Sarcoidosis
Etiological Factors:
![](https://promedscape.com/wp-content/uploads/2023/07/chronic-infl4.png)
- Persistent infection by microbes that are difficult to eradicate.
- Mycobacteria tuberculosis, Treponema pallidum, certain viruses and fungi.
- They elicit a T lymphocyte-mediated immune response called delayed type hypersensitivity.
- Immune mediated inflammatory diseases (hypersensitivity diseases).
- Diseases that are caused by excessive and inappropriate activation of immune system.
- Immune reactions develop against the affected person’s own tissue, leading to autoimmune diseases.
- Autoantigens evoke a self-perpetuating immune reaction that results in tissue damage and persistent inflammation.
- Immune mediated diseases may show morphological patterns of mixed acute and chronic inflammation b/c they are characterized by repeated bouts of inflammation.
e.g.
– RA, IBD.
- Prolonged exposure to potentially toxic agents.
e.g.
- Non degradable exogenous materials such as inhaled particulate silica, which can induce a chronic inflammatory response in the lungs (silicosis).
- Endogenous agents such as cholesterol crystals, which may contribute to atherosclerosis.
- Unresolved acute inflammation:
- When acute inflammation can not be resolved either b/c of persistence of the injurious agent or b/c of interference in the normal healing process, it leads to chronic inflammation.
- Others.
- Neurodegenerative disorders e.g. Alzheimer disease
- Atherosclerosis
- Metabolic syndrome
- Type 2 diabetes
- Some forms of cancer in which inflammatory reactions promote tumor development.
![](https://promedscape.com/wp-content/uploads/2023/07/chronic-ifnl-5.png)
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