B43-44 Silent Seropositive RA: Exudative Pleural and Pericardial Effusions as the Initial Presentation for Rheumatoid Arthritis

Abstract Rheumatoid arthritis (RA) is a systemic autoimmune disease that presents as inflammatory polyarthritis, though extra-articular manifestations can develop years after disease onset. Pulmonary manifestations typically arise within five years of diagnosis, with symptomatic unilateral pleural effusions in 3-5% of patients. Pericardial effusions in RA are considerably less common, rarely presenting as symptomatic pericardial disease. We present a case of a 74-year-old transgender female with history of renal cell carcinoma status post right nephrectomy, recently hospitalized for large pericardial effusion with early signs of tamponade requiring pericardial drain. She now presented with dyspnea on exertion, found to have acute hypoxic respiratory failure with oxygen saturation of 95% on four liters nasal cannula. CT chest showed moderate left-sided pleural effusion, recurrent small pericardial effusion, and enlarged prevascular lymph nodes, without interstitial lung disease. Pleural fluid studies were exudative, with elevated pleural fluid to serum fluid protein ratio of 0.6, glucose 87 mg/dL, and LDH 262 IU/L. Cytology confirmed benign mesothelial cells with acute and chronic inflammatory background. Infectious studies were negative, including bacterial, fungal and AFB cultures without growth. Autoimmune work up revealed negative anti-nuclear (ANA) antibody, but elevated rheumatoid factor (RF) of 32 (normal 14 IU/mL) and anti-cyclic citrullinated peptide (CCP) IgG antibody 250 (normal20 units). She briefly required a left sided pigtail catheter to facilitate drainage, with resolution of symptoms upon initiation of immunosuppressive therapy. Pleural effusions in RA are often asymptomatic and incidentally detected. ANA-negative RA occurs in up to 30% of patients and is associated with delayed diagnosis and treatment initiation, emphasizing the importance of comprehensive serologic testing when there is high clinical suspicion. High RF and anti-CCP titers are linked to higher risk of extra-articular complications, including pleural and pericardial effusions. Pleural effusions in RA are typically exudative, unilateral, and more often left-sided, as seen in this case. Notably, this patient’s pleural fluid characteristics were atypical for a classic rheumatoid effusion, which usually presents with LDH 700 IU/L and glucose 60 mg/dL, further complicating diagnosis. She was ultimately diagnosed with RA-associated serositis, a rare initial presentation RA consisting of pericardial and pleural exudative effusions without synovitis. Extra-articular manifestations may precede synovitis in RA, and severity of joint disease does not predict the likelihood of complications such as serositis. This case underscores the importance of including RA in the differential diagnosis of unexplained effusions, even in the absence of classic articular disease. This abstract is funded by: None