Sarcoidosis was once considered a rare disease. We now know that it is a common chronic illness that appears all over the world. Indeed, it is the most common of the fibrotic lung disorders, and occurs often enough in the United States for Congress to have declared a national Sarcoidosis Awareness Day in 1990.

Anyone can get sarcoidosis. It occurs in all races and in both sexes. Nevertheless, the risk is greater if you are a young black adult, especially a black woman, or of Scandinavian, German, Irish, or Puerto Rican origin. No one knows why.

Because sarcoidosis can escape diagnosis or be mistaken for several other diseases, we can only guess at how many people are affected. The best estimate today is that about 5 in 100,000 white people in the United States have sarcoidosis. Among black people, it occurs more frequently, in probably 40 out of 100,000 people.

Overall, there appear to be 20 cases per 100,000 in cities on the east coast and somewhat fewer in rural locations. Some scientists, however, believe that these figures greatly underestimated the percentage of the U.S. population with sarcoidosis.

Sarcoidosis mainly affects people between 20 to 40 years of age. White women are just as likely as white men to get sarcoidosis, but the black female gets sarcoidosis two times as often as the black male.

Sarcoidosis also appears to be more common and more severe in certain geographic areas. It has long been recognized as a common disease in Scandinavian countries, where it is estimated to affect 64 out of 100,000 people. But it was not until the mid-1940's-when a large number of cases were identified during mass chest x-ray screening for the Armed Forces-that its high prevalence was recognized in North America.

What Sarcoidosis is Not

Much about sarcoidosis remains unknown. Nevertheless, if you have the disease, you can be reassured about several things.

Sarcoidosis is usually not crippling. It often goes away by itself, with most cases healing in 24 to 36 months. Even when sarcoidosis lasts longer, most patients can go about their lives as usual.

Sarcoidosis is not a cancer. It is not contagious, and your friends and family will not catch it from you. Although it can occur in families, there is no evidence that sarcoidosis is passed from parents to children.

Some Things We Don't Know About Sarcoidosis

Sarcoidosis is currently thought to be associated with a abnormal immune response. Whether a foreign substance is the trigger is a chemical, drug, virus, or some other substance; how exactly the immune disturbance is caused are not known.

Researchers supported by the National Heart, Lung, and Blood Institute are trying to solve some of these mysteries. Among the research questions they are trying to answer are:

• Does sarcoidosis have many causes, or is it produced by a single agent?

• In which body organ does sarcoidosis actually start?

• How does sarcoidosis spread from one part of the body to another?

• Do heredity, environment, and lifestyle play any role in the appearance, severity, or length of the disease?

• Is the abnormal immune response seen in patients a cause or an effect of the disease?

• How can sarcoidosis be prevented?

Course of the Disease

In general, sarcoidosis appears briefly and heals naturally in 60 to 70 percent of the cases, often without the patient knowing or doing anything about it. From 20 to 30 percent of sarcoidosis patients are left with some permanent lung damage. In 10 to 15 percent of the patients, sarcoidosis can become chronic.

When either the granulomas or fibrosis seriously affect the function of a vital organ-the lungs, heart, nervous system, liver, or kidneys, for example-sarcoidosis can be fatal. This occurs 5 to 10 percent of the time.

No one can predict how sarcoidosis will progress in an individual patient. But the symptoms the patient experiences, the doctor's findings, and the patient experiences, the doctor's findings, and the patient's race can give some clues.

For example, a sudden onset of general symptoms such as weight loss of feeling poorly are usually taken to mean that the course of sarcoidosis will be relatively short and mild. Dyspnea and possibly skin sarcoidosis often indicate that the sarcoidosis will be more chronic and severe.

White patients are more likely to develop the milder form of the disease. Black people tend to develop the more chronic and severe form.

Sarcoidosis rarely develops before the age of 10 or after the age of 60. However, the illness-with or without symptoms-has been reported in younger as well as in older people. When symptoms do appear in these age groups, the symptoms are those that are more general in nature, for example, tiredness, sluggishness, coughing and a general in nature, for example, tiredness, sluggishness, coughing, and a general feeling of ill health.