Studies have shown that some ethnic groups are at a greater risk than others for sarcoidosis. The best estimate today is that about 5 in 100,000 whites in the United States have sarcoidosis. The lifetime risk of sarcoi-dosis is 0.85 percent for U.S. whites and 2.44 percent for U.S. blacks. It is also more common in whites of north-ern European descent than in other whites. Swedes, Danes and U.S. blacks have the highest prevalence rates in the world.
Sarcoidosis can be completely symptomless.
Doctors will use tests such as X-rays, blood tests, and pulmonary function tests to diagnose sarcoidosis, and usually confirm the diagnosis through a biopsy. The disease must be differentiated from others with which symptoms may overlap, including certain malignancies, tuberculosis, and other infections. The cause of sarcoidosis is unknown, and no known infectious agent is currently a candidate. It has been suggested that an exaggerated immune system defense reaction against some unknown substance may trigger the condition and that there may be contributing genetic factors. The remain-ing patients live with moderate degrees of impairment and disability.