Low‐Titre ANA Late‐Onset Systemic Lupus Erythematosus Presenting With Pleural Effusion and Markedly Elevated Pleural Adenosine Deaminase Mimicking Tuberculous Pleuritis

ABSTRACT

Pleural effusion with markedly elevated adenosine deaminase (ADA) levels is commonly associated with tuberculous pleuritis but may occur in other conditions. We report a case of low‐titre ANA late‐onset systemic lupus erythematosus (SLE) presenting with pleural effusion and markedly elevated ADA levels mimicking tuberculosis. A 78‐year‐old man with pneumoconiosis presented with fever, cough, and progressive pleural effusion. Pleural fluid analysis revealed lymphocyte‐predominant exudative effusion with markedly elevated ADA levels. Tuberculous pleuritis was initially suspected, but microbiological tests were negative. The patient developed thrombocytopenia, renal dysfunction, and altered consciousness. Immunological findings showed hypocomplementemia and elevated anti–double‐stranded DNA antibodies despite low‐titre ANA. Corticosteroid therapy led to rapid improvement, confirming the diagnosis of late‐onset SLE. Clinicians should consider autoimmune diseases when tuberculosis is not microbiologically confirmed.