Lupus erythematosus profundus is a rare inflammatory disorder of subcutaneous fat in patients with lupus ery-thematosus. Previous reports suggested that plasmacytoid dendritic cells, which expressed CD123 and CD303 antigens, play a central proinflammatory role in the patho-genesis of lupus erythematosus. To find the factors that determine the response to treatment, we analysed 23 skin specimens from the patients with lupus erythematosus profundus. The patients with considerable lymphocytic inflammation with high percentages of CD123+ cells in dermis and subcutaneous fat significantly responded to the systemic corticosteroid therapies. On the other hand, the patients with minor lymphocytic inflammation with low percentages of CD123+ cells showed poor response to treatments. The mean percentage of CD123+ cells in patients who showed good response to therapy was significantly higher than those that showed poor response (p = 0.027). These results suggest that the clinical response to treatment of lupus erythematosus profundus could be predicted from the histological features.