Diagnosis of a chronic leg ulcer should be performed early and in a structured manner by means of anamnesis, clinical examination, bacteriological smear and vascular diagnostics. About 10 – 20 % of the leg ulcers are caused by rare diseases. Ulcerating skin tumours can be misinterpreted as vascular wounds. This might lead to a deterioration in the overall prognosis of the patient. In the presence of rheumatoid arthritis or other underlying inflammatory diseases, a pyoderma gangrenosum should be considered. A positive travel history to endemic areas may be indicative of leishmaniasis if the ulceration is found in an unusual localization or if the patient is young. An interdisciplinary case discussion in case of complicated or unclear wounds is recommended for the development of an individual treatment concept.