Sarcoidosis is a multisystem disorder that most often affects individuals between 20 and 40 years of age. Females appear to be affected more frequently than males. Sarcoidosis is characterized by the abnormal formation of inflammatory masses or nodules (granulomas) consisting of certain granular white blood cells (modified macrophages or epithelioid cells) in certain organs of the body. The granulomas that are formed are thought to alter the normal structure of and, potentially, the normal functions of, the affected organ(s), causing symptoms associated with the particular body system(s) in question. In individuals with sarcoidosis, such granuloma formation most commonly affects the lungs. However, in many cases, the upper respiratory system, lymph nodes, skin, and/or eyes may be involved. In addition, in some cases, other organs may be affected, including the liver, bone marrow, spleen, musculoskeletal system, heart, salivary glands, and/or nervous system (i.e., central or peripheral nervous system).
The range and severity of symptoms associated with sarcoidosis vary greatly, depending upon the specific organ(s) involved and the degree of such involvement. In some cases, the symptoms of sarcoidosis may begin suddenly (acute), sometimes severely, and subside in a relatively short period of time (self limited). Acute sarcoidosis is often characterized by fatigue, fever, generalized muscle aches, difficulty breathing (dyspnea), joint pain, swollen glands, skin eruptions, eye irregularities, and/or other symptoms. In the subacute form, affected individuals may experience no symptoms (asymptomatic), even with organ involvement. In the chronic form of sarcoidosis, symptoms may appear slowly and subtly, and may persist or recur over a long time span. Initial symptoms of the chronic form of the disorder may include difficulty breathing (dyspnea), dry cough, limited airflow, and other respiratory abnormalities. Symptoms associated with other organ involvement may follow.
The exact cause of sarcoidosis is not known. However, possible infectious, environmental, genetic, and immunological factors are under investigation as potential causes of the disorder.