Sarcoidosis is characterized by a persistent nodular inflammation of the involved tissues.
Lungs, lymph nodes, eyes, skin, liver and spleen are most often involved, but almost any tissue or organ of the body may be affected. The cause of sarcoidosis is still unknown. It was once thought to be a form of tuberculosis but this is now known not to be the case. Most evidence suggests that sarcoidosis represents a reaction of the body to some as yet unidentified environmental agent or agents. Viruses have been implicated, but definite proof is lacking.