# From Dyspnea to Diagnosis: Neutrophilic Pleural Effusion With Elevated Adenosine Deaminase As the First Clue to New-Onset Rheumatoid Arthritis

## TL;DR

A woman's first sign of rheumatoid arthritis was a pleural effusion with high adenosine deaminase levels, which can mistakenly suggest tuberculosis.

## Contribution

Highlights that elevated adenosine deaminase in pleural fluid can indicate rheumatoid arthritis, not just tuberculosis.

## Key findings

- A large neutrophil-rich pleural effusion with elevated ADA was the first sign of seropositive rheumatoid arthritis in a 44-year-old woman.
- Early immunosuppression based on serial fluid analysis and serology led to complete radiographic resolution.
- ADA levels must be interpreted in the full clinical context to avoid misdiagnosis and unnecessary anti-tuberculous therapy.

## Abstract

Rheumatoid arthritis (RA) rarely announces itself with a pleural effusion, yet when it does, the biochemical and pleural fluid profile often leads to a suspicion of infectious etiology at first. We describe a 44‑year‑old woman whose initial manifestation of seropositive RA was a large, unilateral, neutrophil‑rich, adenosine‑deaminase (ADA)-positive pleural effusion. The case draws attention to a diagnostic pitfall: elevated pleural fluid ADA-although classically associated with tuberculous pleuritis-can also occur in rheumatoid pleuritis, highlighting that ADA levels must be interpreted in the full clinical context and should not, by themselves, prompt initiation of anti-tuberculous therapy. By combining serial fluid analysis with targeted serology, we avoided unnecessary antimycobacterial therapy, initiated immunosuppression early, and achieved complete radiographic resolution. The report emphasizes the need to identify extra-articular conditions (especially pleural involvement) as potential early indicators of RA development.