Mycobacterium ulcerans infection is found all over the world, mainly in tropical rainforest areas. The natural host and human transmission route of this fungus are still unclear, and insects may be the transmission medium. Skin lesions often occur on the forearms and lower legs. Initially, it is a firm, painless subcutaneous nodule, which ruptures to form a necrotic ulcer with a perforating edge that slowly expands. The surrounding skin is raised, infiltrated and pigmented, and the surface is dry. The bottom of the ulcer is an adherent gray pseudomembrane. Generally, the ulcer is relatively superficial, and some can be deep to the periosteum. It can be divided into the pre-ulcer stage (early stage), ulcer stage, and late ulcer stage. The tissue pathology is different. Culture and animal inoculation are required for diagnosis. Systemic treatment with clofazimine has a good effect,