Buruli ulcer in Benin In a study of 28 patients with Mycobacterium ulcerans infection (Buruli ulcer) in Oinhi, Benin, it became clear that the disease can regress as well as progress, and that patients can have lesions of different stages simultaneously. A system of disease staging was introduced (I = subcutaneous nodule; II = cellulitis; III = ulceration; IV = scar formation). Research to find an effective treatment for this crippling disease is urgently needed. 