Granuloma — Detailed Note

Definition

A granuloma is a small, organized collection of macrophages (epithelioid cells) formed during chronic inflammation. It develops when the body is unable to remove a persistent infection, foreign material, or other harmful substance.

Formation of Granuloma

When a harmful substance remains in the body for a long time:

1. Macrophages gather around the substance.
2. Macrophages become larger and are called epithelioid cells.
3. Some macrophages join together to form multinucleated giant cells.
4. Lymphocytes surround these cells.
5. Sometimes, the center develops necrosis (dead tissue).

Main Features

• Collection of epithelioid macrophages
• Presence of multinucleated giant cells
• Surrounding lymphocytes
• Usually associated with chronic inflammation
• May be caseating or non-caseating

3 Causes of Granuloma

1. Tuberculosis (TB)

• Caused by Mycobacterium tuberculosis.
• It commonly produces caseating granulomas.
• The center of the granuloma contains caseous necrosis, which looks like soft, cheese-like material.
• Commonly affects the lungs, but can affect other organs.

2. Leprosy

• Caused by Mycobacterium leprae.
• It produces granulomatous inflammation, especially in the skin and peripheral nerves.
• Granulomas form as the immune system attempts to control the bacteria.
• It may cause skin lesions and nerve damage.

3. Fungal infections

• Some fungi, such as Histoplasma, can produce granulomas.
• The immune system forms granulomas to contain the fungal organisms.
• They commonly involve the lungs and may resemble tuberculosis.