A 47-year-old male was referred to our hospital with persistent high fever. He had received antibiotics (ASPC) for the diagnosis of acute infectious disease, which failed to respond, and subsequently developed marked lymphocytopenia and thrombocytopenia. During his hospitalization, hypoxic respiratory failure rapidly developed. A bone marrow aspiration revealed marked hemophagocytosis, leading to the tentative diagnosis of opportunistic respiratory infection associated with malignant histiocytosis. Treatment for suspected malignancy and Pneumocystis carinii pneumonia was commenced. However, because of the initial lack of response to ASPC, generalized skin rashes without an ordinary stick wound which had diminished before the hospitalization, and a history of working outdoors in a nearby mountain area, the possibility of new type tsutsugamushi disease was strongly suggested. Intravenous administration of minocycline promptly improved his symptoms and laboratory data. The diagnosis was confirmed by a significant increase in the titer of antibody to Rickettsia tsutsugamushi. The thrombocytopenia was considered to have been caused by co-existent hemophagocytic syndrome.
