[A case of tuberculous pericarditis, the diagnosis of which was complicated by the delay in the rise of adenosine deaminase in the pericardial effusion].

An 81-year-old man was admitted to our hospital because of pericardial effusion and sputum PCR positive for Mycobacterium (M.) tuberculosis. Since adenosine deaminase (ADA) value of the pericardial effusion was not high and the sputum smear and culture were negative, anti-tuberculous therapy was not started. Two months later he was admitted again because of high fever and cardiomegaly. Chest computed tomography showed deterioration and the sputum culture revealed M. tuberculosis. The ADA value of the pericardial effusion which was not high at the first admission, was elevated in the second admission, and the diagnosis was made as tuberculous pericarditis two months later. We had better start anti-tuberculous therapy at the first admission, in spite of low value of ADA, as his pericardial effusion showed lymphocyte predominance.