Rapid development of severe osteoarthritis associated with osteoid osteoma in a young girl

A 52-year-old woman with a seven-year history of rheumatoid arthritis (RA) was transferred to our department with chronic renal failure to undergo hemodialysis. She had been treated with prednisolone for a long time, and had renal amyloidosis secondary to RA. During her hospitalization, a left pleural effusion developed. Pleural fluid cultured positive for Cryptococcus neoformans (CN), and the CN antigen was detected in both pleural fluid and serum. Chest computerized tomography revealed an infiltrate shadow in the left lower lung field suggestive of CN infection. This was successfully treated with anti-fungal agents. Pleural effusion is an unusual manifestation of pulmonary cryptococcosis. We should consider a diagnosis of CN infection when pleural effusion is observed in compromised patients such as those receiving a long-term corticosteroid treatment.