Granuloma
A granuloma is an aggregation of macrophages (along with other cells) that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate.[1] Such substances include infectious organisms including bacteria and fungi, as well as other materials such as foreign objects, keratin, and suture fragments.[2][3][4][5]
"Granulomatous" and "Granulomatous reactions" redirect here. For the Interstitial granulomatous drug reaction, see Interstitial granulomatous drug reaction.Granuloma
Granuloma without necrosis in a lymph node of a person with sarcoidosis
Granuloma with central necrosis in a lung of a person with tuberculosis: Note the Langhans-type giant cells (with many nuclei arranged in a horseshoe-like pattern at the edge of the cell) around the periphery of the granuloma. Langhans-type giant cells are seen in many types of granulomas and are not specific for tuberculosis.
Diseases with granulomas[edit]
Tuberculosis[edit]
Mycobacterium tuberculosis can cause the granulomas of tuberculosis which tend to contain necrosis ("caseating tubercules"), but non-necrotizing granulomas may also be present.[8] Multinucleated giant cells with nuclei arranged like a horseshoe (Langhans giant cell) and foreign body giant cells[9] are often present, but are not specific for tuberculosis. A definitive diagnosis of tuberculosis requires identification of the causative organism by microbiologic cultures.[10]
Aquarium granuloma[edit]
The other Mycobacterium species, Mycobacterium marinum can cause a rare infection known as "aquarium granuloma."[11]
Schistosomiasis[edit]
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.
Histoplasmosis[edit]
Granulomas are seen in most forms of histoplasmosis (acute histoplasmosis, histoplasmoma, chronic histoplasmosis). Histoplasma organisms can sometimes be demonstrated within the granulomas by biopsy or microbiological cultures.[2]
Cryptococcosis[edit]
When Cryptococcus infection occurs in persons whose immune systems are intact, granulomatous inflammation is typically encountered. The granulomas can be necrotizing or non-necrotizing. Using a microscope and appropriate stains, organisms can be seen within the granulomas.[10]
Cat-scratch disease[edit]
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. Organisms are usually difficult to find within the granulomas using methods routinely used in pathology laboratories.
Rheumatic fever[edit]
Rheumatic fever is a systemic disease affecting the periarteriolar 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.
Granulomas associated with vasculitis[edit]
Certain inflammatory diseases are characterised by a combination of granulomatous inflammation and vasculitis (inflammation of the blood vessels). Both the granulomas as well as the vasculitis tend to occur in association with necrosis. Classic examples of such diseases include granulomatosis with polyangiitis and eosinophilic granulomatosis with polyangiitis.