The cause of Whipple disease is infection with the bacterium Tropheryma whipplei. This bacterium initially affects the mucosal lining of your small intestine, forming small lesions within the intestinal wall. The bacterium also damages the fine, hair-like projections (villi) that line the small intestine. With time, the infection can spread to other parts of your body.

Not much is known about the bacterium. Although it seems readily present in the environment, scientists don't really know where it comes from or how it's transmitted to humans. Not everyone who carries the bacterium develops the disease. Some researchers believe that people with the disease may have a genetic defect in their immune system response that makes them more susceptible to becoming ill when exposed to the bacterium.

Whipple disease is extremely uncommon, affecting fewer than one in 1 million people.

Oct. 24, 2015