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When
was sarcoidosis discovered? What causes sarcoidosis? The cause of sarcoidosis is not known; however, this diagnosis is what is known as a "diagnosis of exclusion". This term is used for a disease that has no known cause, but mimics other disorders that must first be excluded before establishing the diagnosis of sarcoidosis. For example, there is a lung disease called hypersensitivity pneumonia (HP), which is also referred to as allergic alveolitis that must be excluded. This is an acute or chronic granulomatous lung disorder that is caused by an immune response to a variety of organic substances (antigens) that include bird proteins, spores of microbes, or airborne bacteria. There are over 300 agents that have been reported to cause this disorder. Hypersensitivity pneumonia may occur as a reaction to protein material from pigeons (pigeon breeder’s disease) or parakeets, from contaminated humidifiers or air conditions in the home, office or automobile (humidifier lung), or from mists created from contaminated water such as a basement shower or sauna. Hypersensitivity pneumonia may have the same symptoms and identical chest x-ray findings as sarcoidosis. A blood serology test that is positive for the causative agent can diagnose hypersensitivity pneumonia. Avoidance of the causative agent can result in resolution of the illness. Sometimes, a brief course of corticosteroid treatment is utilized in the acute form of hypersensitivity and a longer course for the chronic form. Chronic fungal infections of the lung such as histoplasmosis can also mimic sarcoid in certain situations, and these disorders must also be excluded. The fungal disorders are treated with a long course of specific types of antibiotics. Exposures to certain metal dusts can cause a disorder indistinguishable from sarcoidosis. In the late 1940’s there was a group of patients with "sarcoid" in the region of Salem, Massachusetts. It was even called "Salem Sarcoid". Dr. Harriet Hardy investigated the disorder and discovered that it occurred only in employees working in a factory where the metal, beryllium, was used to increase the duration of use of fluorescent light bulbs. This disorder was called berylliosis. The use of beryllium in fluorescent lights was stopped after the description of the disorder and no more cases of "Salem Sarcoid" occurred. Avoiding exposure to beryllium can result in resolution of the acute form of the illness, although, a course of corticosteroid treatment is generally utilized. The chronic form is more difficult to treat.
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