Sarcoidosis

What Is It?

Sarcoidosis is an illness of unknown cause that causes tiny islands of inflammatory cells to form throughout the body. These microscopic groups of cells are called granulomas, and they are especially common in the lungs, lymph nodes, skin, eyes and liver.

Sometimes, these granulomas cause very little damage, so the person with sarcoidosis does not have any symptoms of illness. In other cases, however, the granulomas produce large areas of inflammation and scarring that can interfere with an organ's normal functions. Although most people with sarcoidosis eventually recover, a few develop forms of the illness that are long-lasting (chronic) and get worse with time.

Sarcoidosis can affect almost any body organ, but the most common target is the lung.

Although doctors do not know the exact cause of sarcoidosis, there is strong evidence that the illness involves an abnormal immune reaction. For example, it is known that the granulomas contain cells from the immune system, particularly a type called helper-inducer T cells. Some experts believe that the abnormal immune reaction of sarcoidosis may be triggered by an infection. Others suspect that the illness may follow exposure to an allergen (allergy-producing agent) in the environment. In addition, genetic (inherited) factors probably play some role in increasing a person's risk of developing the illness.

In the United States, sarcoidosis affects about 5 to 10 out of every 100,000 whites and about 36 out of every 100,000 blacks. Other groups with a higher risk of developing sarcoidosis are Scandinavians, Irish, British and Japanese. In general, women are affected more often than men, and about 75% of all those affected are younger than age 40.

Symptoms

Some people with sarcoidosis do not have any symptoms. Others simply feel tired and weak. Still others have nonspecific symptoms, such as fever, poor appetite, night sweats, joint pain or aching muscles. Symptoms vary widely because the disease affects different parts of the body in different people. Among those who see their doctors for more specific symptoms, more than 90% have problems involving the lungs. The first signs are usually a dry cough and shortness of breath. Later, there may also be wheezing, chest pain and, rarely, a cough that brings up bloody mucus. Rarely, in severe cases, lung function may become so poor that the person cannot perform even the simple, routine tasks of daily life.

Other symptoms of sarcoidosis are less common than lung symptoms. They can include: