Adult-onset Still's disease-like manifestation accompanied by the cancer recurrence after long-term resting state.

A 72-year-old woman presented 9 months ago with skin rash on her bilateral forearms, which was followed by intermittent high fever, and stiffness and swelling of her bilateral fingers. She was diagnosed with seronegative rheumatoid arthritis (RA). She had a past history of breast cancer and had undergone breast preservation surgery 13 years previously. During admission in our hospital, she developed high fever and leukocytosis with a relapsing skin rash, sore throat, polyarthralgia and increased levels of serum ALT/AST and ferritin, all of which fulfilled Yamaguchi's criteria for adult-onset Still's disease (AOSD). While we tried to exclude other diseases that may show AOSD-like manifestations, pancytopenia rapidly developed and bone marrow biopsy strongly suggested the diagnosis of macrophage activating syndrome (MAS). Accordingly, steroid pulse therapy was begun, followed by oral glucocorticoid therapy. Thereafter, all of her symptoms improved, but systemic rash, inflammatory signs and pancytopenia gradually progressed. The results of bone marrow pathology, which returned 2 weeks after the beginning of treatment, revealed hemophagocytosis with CK7-positive/CK20-negative atypical cells that suggested recurrence of breast cancer in the bone marrow, thus all of her AOSD-like symptoms were considered to be paraneoplastic manifestations of late-onset metastatic breast cancer. She was treated successfully with chemotherapy. When we see the patients showing AOSD-like symptoms with a history of malignancy, we should consider the possibility of paraneoplastic syndrome due to cancer recurrence.