[A CASE OF PROBABLE LATE-ONSET SYSTEMIC LUPUS ERYTHEMATOSUS WHERE THE INITIAL MANIFESTATION WAS A UNILATERAL PLEURAL EFFUSION].

A 74-year-old man developed with left pleural effusion and was suspected of benign asbestos pleural effusion and tuberculous pleurisy. Because of elevation of ADA level in the pleural effusion, diagnostic treatment for tuberculous pleurisy by anti-tuberculosis drugs was performed. However, right pleural effusion, cutaneous/mucosal lesions, leukocytopenia, and fever elevation occurred. The pathology of skin biopsy was consistent with systemic lupus erythematosus (SLE). Since clinical findings did not improve even after discontinuation of all drugs, he received steroid therapy was started and clinical findings improved. He was suspected of late-onset SLE. In conclusion, lupus pleurisy should also be differentiated when pleural effusion is seen in older. Late-onset SLE and drug-induced lupus should be carefully differentiated based on the clinical course.