Sarcoidosis
Sarcoidosis is a multisystem inflammatory disease in which granulomas—clusters of immune cells—form in organs, most often the lungs and lymph nodes.
Granuloma: A localized collection of immune cells that forms in response to persistent inflammation or material the body cannot readily clear. Granulomas are the defining tissue lesions of sarcoidosis.
Pulmonary sarcoidosis: Sarcoidosis involving the lungs, which occurs in most people with the disease. Lung involvement drives many presentations and is commonly assessed with imaging and pulmonary-function tests.
Lymphadenopathy: Abnormal enlargement of lymph nodes, usually due to infection, inflammation, or malignancy. Enlarged intrathoracic lymph nodes are a frequent imaging finding in sarcoidosis.
Tuberculosis: An infectious disease caused by Mycobacterium tuberculosis, usually affecting the lungs. Tuberculosis can produce granulomas and must be considered before diagnosing sarcoidosis.
Sarcoidosis susceptibility: The inherited and environmental factors that influence the likelihood of developing sarcoidosis. Genetic predisposition is established, but the combination of factors that triggers disease remains unclear.
Noncaseating granuloma: A granuloma without the central tissue necrosis typical of caseating granulomas. Sarcoidosis commonly produces noncaseating granulomas, though this finding alone is not diagnostic.
Löfgren syndrome: An acute sarcoidosis presentation featuring bilateral ankle arthritis, erythema nodosum, and bilateral hilar lymphadenopathy. This recognizable combination can strongly support a sarcoidosis diagnosis.
Erythema nodosum: An inflammatory condition causing tender red nodules, usually on the shins. It can accompany acute sarcoidosis, especially Löfgren syndrome.
Histoplasmosis: An infection caused by the fungus Histoplasma, acquired mainly by inhaling spores. Histoplasmosis can resemble sarcoidosis clinically and produce granulomatous tissue inflammation.
Antigen: A molecule or molecular structure that can be recognized by the immune system. The persistent antigen that initiates sarcoidosis has not been identified.