Adenosine deaminase in the diagnosis of tuberculous pericardial effusion

Not long ago, primary tuberculosis was considered a rare disease; now with an increasing incidence worldwide, physicians should relearn many of its basic aspects and manifestations. Pericarditis is a rare finding seen with tuberculosis, but its prognosis is excellent with treatment, so early diagnosis is crucial. Pathogenesis is particularly important, and it must be taken in consideration when interpreting diagnostic tools. Herein we report on a healthy 32-year-old woman who presents with a 1-month history of febrile illness, malaise, and weakness; more recently, she also had resting dyspnea, which was progressively worsening. A positive PPD and an abnormal chest radiograph prompted hospitalization, where she was found to have pulsus paradoxus of 20 mm Hg. The echocardiogram showed diastolic right chamber collapse along with respiratory variation of the mitral inflow, consistent with pericardial tamponade. A pericardiocentesis was performed with resolution of her resting dyspnea; more than 1000 mL of serous fluid drained from the pericardial space over the following 24 hours. Although sputum and pericardial fluid cultures and smear for AFB and other organisms were negative, as well as a negative pericardial fluid PCR for Mycobacterium tuberculosis DNA; an elevated (44.4 U/L [normal, 0 to 18]) adenosine deaminase level in the pericardial fluid was consistent with the probable diagnosis of tuberculous pericardial effusion. The patient was treated with resolution of the clinical syndrome and no recurrence of the effusion thereafter. Adenosine deaminase, an enzyme marker of cell-mediated immune response activity to M tuberculosis that includes activated T-lymphocytes and macrophages, appears in pericardial fluid. The diagnosis of probable tuberculous effusion can be made without demonstration of mycobacterium.