We report a case of Behçet disease developed in myelodysplastic syndrome (MDS). A 72-year-old male who was first seen in thrombocytopenic state in 1984, presented recurrent ulcers on the oral cavity and genitalia since 1985. On admission, his blood test revealed that a platelet count of 1.5×104/μl and a bone marrow aspirate showed dysplasia, including hypersegmented neutrophils, micromegakaryocytes and giant platelets. Chromosome study on the bone marrow cells revealed 47, XY, +8, del(20)(q11), indicating the patient was suffering from MDS with monopathic hematological feature. During the course, folliculitis-like eruption was evident and the patient was diagnosed as having incomplete-form Behçet disease. In the literature a small number of cases has been appeared in which Behçet disease developed in MDS or leukemia, and it is difficult to conclude the correlation between these disorders. Accumulation of similar cases presented here might answer the question. We also discuss a monopathic hematological presentation in MDS.
