The case of a Ph-positive female patient with chronic myeloid leukemia (CML) is reported. The patient presented a cutaneous-mucous picture prior to the appearance of the hemopathy consisting of genitals ulcers, buccal aphthae and nodular cutaneous lesions the study of which demonstrated panniculitis. The lesions improved with the administration of low doses of prednisone and colchicine. The CML evolved to a blastic crisis of a monocytic phenotype at 14 months of diagnosis leading to death of the patient. The cutaneous-mucous picture was catalogued as Becçet disease (BD) according to the criteria of the International Study Group for Behçet Disease. Given the lack of serologic tests or pathognomonic histologic lesions the difficulty in the diagnosis of BD is commented upon and the differential diagnosis of this disease, particularly with respect to the Sweet syndrome, is discussed.