Mycetoma usually starts as a small, painless bump under the skin. The bump grows slowly over months or years. Over time, small openings may form on the skin and drain fluid. This fluid contains tiny particles called "grains."
Grains are made up of the bacteria or fungi causing the infection. They can be white, yellow, red, brown, or black. The foot is the most common place to get mycetoma. This is why the infection is sometimes called "Madura foot."
In serious cases, the infection can spread to deeper tissue and bone. This can damage parts of the body and make it hard to move or use the affected area. In very serious cases, the disease can be life-threatening. Pain is usually mild at first but can get worse over time.