MEDICAL MYSTERY: For 25 years, Bernie Mac suffered from sarcoidosis, a poorly understood disease that typically affects the lungs and may have played a role in his untimely death.
AP PHOTO/CHRIS PIZZELLO

Comedian Bernie Mac died on Saturday (August 9) of complications from pneumonia. In the coverage of his death, the media has reported that in 1983, doctors diagnosed him with a mysterious ailment called sarcoidosis.

His publicist says that his three-week battle with pneumonia and his sarcoidosis were unrelated, and CNN reported earlier this week that Mac said his sarcoidosis had entered remission in 2005. But it can be fatal: Sarcoidosis of the heart and lungs was implicated in the death of pro football Hall of Famer, Reggie White, in 2004.

So what is sarcoidosis?

People with the disease typically develop shortness of breath or a dry cough as inflammation cuts down on their lung capacity. The disease—which may infect up to a million people worldwide—affects ethnic groups differently. For example, in 80 to 90 percent of Caucasians who develop it, it simply disappears over time, even without treatment. Meanwhile, in African-Americans, the disease progresses more aggressively, causing more symptoms and resulting in more hospital visits and longer courses of treatment.

Scientific American.com talked to Om Sharma, a sarcoidosis expert at the LAC+U.S.C. Medical Center, to find out more about the illness. An edited interview transcript follows.

What is sarcoidosis?
It's an inflammatory lung disease. The cause of this inflammation is not known, but it almost always affects the lungs first. Ninety percent of the patients have lung involvement, but sarcoidosis can affect any organ in the body--lungs, skin, eyes, heart, brain, bones.

Most of the sarcoidosis patients go to a doctor because of shortness of breath or dry cough or maybe their chest X-ray is found to abnormal during a routine examination. The abnormality that is caused by sarcoidosis is quite typical: an enlargement of the glands in the lungs and scar tissue in the lungs.

What are the symptoms as the disease progresses?
In the beginning, it may be shortness of breath while playing a game of tennis or something. But, later on you might get shortness of breath by just walking a few blocks. And then later you might get shortness of breath while just doing housework. The same can happen to the cough, if it is mild. So, those are symptoms of the lung disease.

If you get skin sarcoidosis, you get lesions on the skin…. They don't go away--and they may progressively get worse. If someone gets sarcoidosis of the eye, then they have blurry vision or redness of the eyes and pain in the eyes. If it's not treated, one could get even blindness or glaucoma. If sarcoidosis affects the liver, then liver function could become abnormal. So, symptoms of the disease depend on the organ involved. But, most of the patients have lung disease.