The authors describe a case of a 67-year-old man with typical lesions of erythema elevatum diutinum involving also oral mucosa and showing Koebner's isomorphic phenomenon. Before presentation the patient suffered from exulcerated plaques with seropurulent secretion which left macular hypo- and hyper-pigmented areas on extensor sites of the limbs resembling pyoderma gangrenosum scars. During the treatment with diaminodiphenylsulphone melena occurred, which could represent a side effect of sulfone (unpublished observation). Therapy with OH-chloroquine and prednison had only a partial effect on clinical symptomatology.

        Key words: erythema elevatum diutinum - mucosal lesion - Koebner's phenomenon - pyoderma gangrenosum - diamindiphenylsulphone - melena