A 44-year-old Japanese female with recurrent pleuritis.

Laboratory tests showed a slightly increased white blood cell count (8,800/mm 3 ) and increased C-reactive protein (11.13 mg/dl). Other blood tests including liver enzymes and renal function were within normal ranges. The urine was negative for Legionella pneumophila and Streptococcus pneumoniae antigen tests. Further laboratory investigation, including immunoglobulin levels, rheumatoid factor, antinuclear antibodies and antineutrophilic cytoplasmic antibodies were within normal ranges. Chest radiography showed a left pleural effusion ( fig. 1 ). A CT scan of the chest revealed a small left pleural effusion and passive atelectasis of the left lower lobe ( fig. 2 ). The left pleural effusion was not large enough to perform a diagnostic thoracentesis. What is your diagnosis? Clinical Presentation – Case Report