Pleural fluid analysis demonstrated a lymphocyte-predominant exudative effusion with elevated adenosine deaminase levels, raising suspicion for tuberculous pleuritis despite repeatedly negative acid-fast bacilli smears and cultures, a well-recognized limitation in tuberculous pleuritis given the paucibacillary burden and slow growth of <i>Mycobacterium tuberculosis</i>. The gene discussed is ADA; the disease is pleural tuberculosis.