Sarcoidosis is an autoimmune disease that leads to inflammation, usually in your lungs, skin, or lymph nodes. It starts as tiny, grain-like lumps, called granulomas. Sarcoidosis can affect any organ in your body. No one is sure what causes sarcoidosis. It affects men and women of all ages and races. It occurs mostly in people ages 20 to 50, African Americans, especially women, and people of Northern European origin. Many people have no symptoms. If you have symptoms, they may include: cough, shortness of breath, weight loss, night sweats, and fatigue. Tests to diagnose sarcoidosis include chest x-rays, lung function tests, and a biopsy. Not everyone who has the disease needs treatment. If you do, prednisone, a type of steroid, is the main treatment.