Granuloma

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]

In leprosy, granulomas are found in the skin and tend to involve nerves. The appearance of the granulomas differs according to the precise type of leprosy.

The other Mycobacterium species, Mycobacterium marinum can cause a rare infection known as "aquarium granuloma."[11]

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.

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]

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 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 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.

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,[12] 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 those of tuberculosis and other infectious granulomatous diseases. In most cases of sarcoidosis, though, the granulomas do not contain necrosis and are surrounded by concentric scar tissue (fibrosis). Sarcoid granulomas often contain star-shaped structures called asteroid bodies or lamellar structures termed Schaumann bodies, but these structures are not specific for sarcoidosis.[10] Sarcoid granulomas can resolve spontaneously without complications or heal with residual scarring. In the lungs, this scarring can cause a condition known as pulmonary fibrosis that impairs breathing. In the heart, it can lead to rhythm disturbances, heart failure, and even death.

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.[13]

Listeria monocytogenes infection in infants can cause potentially fatal disseminated granulomas, called granulomatosis infantiseptica, following in utero infection.

Leishmaniases are a group of human diseases caused by Leishmania genus and transmitted by a sandfly bite can lead to granulomatous inflammation[14] in skin (cutaneous form of the disease) and liver (visceral form), with research suggesting effective granuloma formation to be desirable in the resolution of the disease.[15]

Pneumocystis infection in the lungs is usually not associated with granulomas, but rare cases are well documented to cause granulomatous inflammation. The diagnosis is established by finding Pneumocystis yeasts within the granulomas on lung biopsies.[16]

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. Granulomas may form, though, when food particles or other particulate substances such as pill fragments are aspirated into the lungs. Patients typically aspirate food because they have esophageal, gastric, or neurologic problems. Intake of drugs that depress neurologic function may also lead to aspiration. The resultant granulomas are typically found around the airways (bronchioles), and are often accompanied by foreign body-type, multinucleated giant cells, acute inflammation, or organizing pneumonia. The finding of food particles in lung biopsies is diagnostic.[17]

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.[10]

Granuloma annulare is a skin disease of unknown cause in which granulomas are found in the dermis of the skin, but it is not a true granuloma. Typically, a central zone of necrobiotic generation of collagen is seen, with surrounding inflammation and mucin deposition on pathology.

Granulomatous reaction to nylon suture material

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.[18] In some cases the foreign body can be found and removed even years after the precipitating event.[19]

Childhood granulomatous periorificial dermatitis is a rare granulomatous skin disorder of unknown cause. It is temporary and tends to affect children, usually of African descent.