Makindo Medical Notes

Related Subjects: |Acute Inflammation |Chronic Inflammation

Chronic inflammation is a prolonged inflammatory response that can last for months or years. It results from the failure to eliminate the cause of an acute inflammation, an autoimmune response to a self-antigen, or a chronic irritant of low intensity that persists.

Causes of Chronic Inflammation

• Persistent Infections:
  • Pathogens that evade the immune system or are difficult to eradicate, such as Mycobacterium tuberculosis.
  • Examples: Tuberculosis, chronic hepatitis, and persistent viral infections.
• Autoimmune Diseases:
  • The immune system mistakenly attacks the body's own tissues.
  • Examples: Rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis.
• Prolonged Exposure to Irritants:
  • Environmental or industrial irritants that the body cannot easily eliminate.
  • Examples: Silica in pneumoconiosis, asbestos in asbestosis, and smoking-related lung inflammation.
• Obesity:
  • Adipose tissue produces pro-inflammatory cytokines, contributing to a state of low-grade chronic inflammation.

Mechanisms of Chronic Inflammation

• Cellular Infiltration:
  • Involves the recruitment and accumulation of immune cells, including macrophages, lymphocytes, and plasma cells, at the site of inflammation.
• Fibrosis:
  • Chronic inflammation often leads to the formation of scar tissue (fibrosis) as part of the healing process.
• Angiogenesis:
  • The formation of new blood vessels to supply nutrients and oxygen to the inflamed tissue.
• Granuloma Formation:
  • A granuloma is a collection of immune cells formed to wall off foreign substances that the body is unable to eliminate.
  • Examples: Granulomas in tuberculosis, sarcoidosis, and Crohn's disease.

Key Players in Chronic Inflammation

• Macrophages:
  • Phagocytose pathogens and dead cells.
  • Secrete pro-inflammatory cytokines and growth factors that sustain the inflammatory response and promote tissue repair.
• Lymphocytes:
  • T Cells: Mediate adaptive immune responses, including the activation of macrophages and B cells.
  • B Cells: Differentiate into plasma cells that produce antibodies.
• Plasma Cells:
  • Produce antibodies that contribute to the immune response.
• Cytokines:
  • Pro-inflammatory cytokines (e.g., TNF-α, IL-1, IL-6) play a central role in sustaining inflammation.
  • Anti-inflammatory cytokines (e.g., IL-10, TGF-β) help regulate and resolve inflammation.

Consequences of Chronic Inflammation

• Tissue Damage:
  • Prolonged inflammation can lead to continuous tissue destruction and repair, resulting in scarring and loss of function.
  • Examples: Liver cirrhosis, pulmonary fibrosis, and chronic kidney disease.
• Increased Risk of Cancer:
  • Chronic inflammation creates a microenvironment that can promote tumour development and progression.
  • Examples: Hepatocellular carcinoma (associated with chronic hepatitis), colorectal cancer (associated with inflammatory bowel disease).
• Systemic Effects:
  • Chronic inflammation can contribute to systemic conditions such as cardiovascular disease, metabolic syndrome, and type 2 diabetes.

Diagnosis of Chronic Inflammation

• Clinical Evaluation:
  • Assessment of symptoms, medical history, and risk factors.
• Laboratory Tests:
  • Blood tests for inflammatory markers (e.g., C-reactive protein [CRP], erythrocyte sedimentation rate [ESR]).
  • Measurement of specific cytokines and other biomarkers.
• Imaging Studies:
  • Imaging techniques (e.g., MRI, CT scans) to assess the extent of tissue damage and inflammation.
• Biopsy:
  • Histological examination of tissue samples to identify the presence and extent of inflammation and fibrosis.

Management and Treatment of Chronic Inflammation

• Medications:
  • Anti-inflammatory Drugs: Nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids.
  • Immunosuppressive Drugs: Methotrexate, azathioprine, biologics targeting specific cytokines (e.g., TNF inhibitors, IL-6 inhibitors).
• Lifestyle Modifications:
  • Diet: Anti-inflammatory diets rich in fruits, vegetables, whole grains, and healthy fats.
  • Exercise: Regular physical activity to reduce inflammation and improve overall health.
  • Smoking Cessation: Avoiding tobacco smoke, which exacerbates inflammation.
• Treating Underlying Conditions:
  • Addressing infections, autoimmune diseases, and other underlying causes of chronic inflammation.

Summary

Chronic inflammation is a prolonged and potentially harmful inflammatory response that can result from persistent infections, autoimmune diseases, prolonged exposure to irritants, and other factors. It involves various immune cells and cytokines that contribute to tissue damage, increased cancer risk, and systemic conditions. Effective management involves a combination of medications, lifestyle modifications, and addressing underlying causes.