Sarcoidosis is known for its deep swirls of inflammation called granulomas. This rare disease is probably due to a disruption of the immune system, either by a virus or toxin, and it certainly runs in families. Black people are affected at least three times more often than whites, (35 cases per 100,000 compared to 10 cases per hundred thousand), and this health disparity is most disturbing in terms of outcome, with 13 times more deaths in blacks.

This is because sarcoidosis, which can involve the lungs, lymph nodes, eyes, and brain, tends to affect black people at a younger age (comedian Bernie Mac got the disease in the 1980s), and is far more likely to be chronic or recurrent in blacks, as it was with the famous comedian. Despite Mac's publicist's assertion that his sarcoidosis was in remission and hadn't sickened him since 2005, and despite his statement that it wasn't a factor in his deadly pneumonia, I find this difficult to believe.

My take is that Bernie Mac most likely fell in the group of 20 to 30 percent of sarcoid patients who end up with severely scarred lungs with little reserve lung capacity left. I think Mac's more than two decades battling the disease (the mainstay of treatment is the steroid prednisone) speaks to the probability that his lungs were no longer in shape to fight off bacteria.

Pneumonia doesn't usually kill a 50 year old unless the patient has badly damaged lungs to begin with. In that case, an infection can quickly rifle through the scar tissue and fill what's left of the lungs with pus and fluid. The lungs die, and the patient does too.

I suspect Mac would have wanted his death to serve as a wake-up call for early diagnosis and treatment of chronic lung diseases. Most sarcoidosis can be suspected by the findings on a simple chest x-ray, and though the majority of cases go away without treatment, it still makes sense to be vigilant.

I remember when a physician, Dr. C., came to see me for a routine physical, and the swellings in the center of his chest x-ray made me immediately suspicious of sarcoidosis. When I uttered my concern, he became so anxious that he fainted and fell off his chair. Luckily, he wasn't hurt in the fall, and though he did turn out to have the disease, he was also in the majority group (which unfortunately Mac was not) where it remitted spontaneously.

Dr. C's case, like Mac's, was a reminder to me that sarcoidosis is a puzzling, unpredictable, scary disease that needs to be approached rationally rather than emotionally.

Marc Siegel MD is an internist and associate professor of medicine at the NYU School of Medicine. He is a Fox News Medical Contributor and writes a health column for LA Times, where he examines TV and movies for medical accuracy. Dr. Siegel is the author of False Alarm: the Truth About the Epidemic of Fear (Wiley 2005) and Bird Flu: Everything You Need to Know About the Next Pandemic (Wiley 2006). Read more at www.doctorsiegel.com

Dr. Marc Siegel, a practicing internist, joined FOX News Channel (FNC) as a contributor in 2008..