Granuloma is an inflammation found in many diseases. It is a collection of immune cells known as histiocytes (macrophages). Granulomas form when the immune system attempts to ward off substances it perceives as foreign but is unable to eliminate. Such substances include infectious organisms including bacteria and fungi, as well as other materials such as keratin and suture fragments.
Granulomas are seen in a wide variety of diseases, both infectious and non-infectious.
*Tuberculosis
The granulomas of tuberculosis tend to contain necrosis (“caseating tubercules”), but non-necrotizing granulomas may also be present.
*Leprosy
In leprosy, granulomas are found in the skin and tend to involve nerves.
*Schistosomiasis
Some schistosome ova that are laid in intestinal and urinary venules backwash into the liver via the portal vein causing granuloma formation in the liver.
*Cryptococcosis
When Cryptococcus infection occurs in persons whose immune systems are intact, granulomatous inflammation is typically encountered.
*Cat-scratch disease
Cat-scratch disease is an infection caused by the bacterial organism Bartonella henselae, typically acquired by a scratch from a kitten infected with the organism. The granulomas in this disease are found in the lymph nodes draining the site of the scratch. They are characteristically “suppurative”, i.e., pus forming, containing large numbers of neutrophils.
*Rheumatic Fever
Rheumatic fever is a systemic disease affecting the peri-arteriolar connective tissue and can occur after an untreated Group A Beta-hemolytic streptococcal pharyngeal infection. It is believed to be caused by antibody cross-reactivity.
*Sarcoidosis
Two asteroid bodies in sarcoidosis. H&E stain.
Sarcoidosis is a disease of unknown cause characterized by non-necrotizing (“non-caseating”) granulomas in multiple organs and body sites, most commonly the lungs and lymph nodes within the chest cavity. Other common sites of involvement include the liver, spleen, skin and eyes. The granulomas of sarcoidosis are similar to the granulomas of tuberculosis and other infectious granulomatous diseases.
*Crohn’s disease
Crohn’s disease is an inflammatory condition of uncertain cause characterized by severe inflammation in the wall of the intestines and other parts of the abdomen. Within the inflammation in the gut wall, granulomas are often found and are a clue to the diagnosis.
*Pneumocystis pneumonia
Pneumocystis infection in the lungs is usually not associated with granulomas, but rare cases are well documented to cause granulomatous inflammation.
*Aspiration pneumonia
Aspiration pneumonia is typically caused by aspiration of bacteria from the oral cavity into the lungs, and does not result in the formation of granulomas. However, granulomas may form when food particles or other particulate substances like pill fragments are aspirated into the lungs.
*Rheumatoid arthritis
Necrotizing granulomas can develop in patients with rheumatoid arthritis, typically manifesting as bumps in the soft tissues around the joints (so-called rheumatoid nodules) or in the lungs. [8]
*Granuloma annulare
Granuloma annulare is a skin disease of unknown cause in which granulomas are found in the dermis of the skin. However, it is not a true granuloma. Typically there is a central zone of necrobiotic generation of collagen with surrounding inflammation and mucin deposition on pathology.
*Foreign-body granuloma
A foreign-body granuloma occurs when a foreign body (such as a wood splinter, piece of metal, glass etc.) penetrates the body’s soft tissue followed by acute inflammation and formation of a granuloma.
