Buruli ulcer is an infectious disease caused by Mycobacterium ulcerans. The early stage of the infection is characterised by a painless nodule or area of swelling. This nodule can turn into an ulcer. The ulcer may be larger inside than at the surface of the skin, and can be surrounded by swelling.Buruli ulcer is an ulcerative skin disease caused by the bacterium Mycobacterium ulcerans. It often starts as painless nodules, usually on the arms and legs. These then develop into large ulcers with a whitish-yellow base. Buruli ulcer can be cured with early detection and a combination of antibiotics.