Effusion Unveiled: Impending Cardiac Tamponade as the Initial Manifestation of Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized primarily by inflammatory polyarthritis, although extra-articular manifestations, including pericardial disease, are well recognized. While pericardial effusions are relatively common, large symptomatic effusions causing cardiac tamponade as the initial manifestation of RA are exceedingly rare. We report a 75-year-old woman with hypertension and dyslipidemia who presented with progressive dyspnea and fatigue one month after an episode of right-hand monoarthritis with an initially unrevealing rheumatologic evaluation. Electrocardiography demonstrated low-voltage QRS complexes, and bedside echocardiography revealed a large pericardial effusion with tamponade physiology. She underwent urgent surgical pericardial window, and pericardial fluid analysis excluded infectious and malignant etiologies. Notably, the erythrocyte sedimentation rate and C-reactive protein were both normal, and the fluid met an exudative threshold on protein content alone.Autoimmune testing demonstrated markedly elevated rheumatoid factor (246 IU/mL), positive antinuclear antibody (1:1280), and strongly positive anti-cyclic citrullinated peptide antibodies, supporting a diagnosis of seropositive RA. Treatment with high-dose intravenous methylprednisolone followed by an oral prednisone taper resulted in significant clinical improvement. This case highlights that cardiac tamponade may precede the classic manifestations of RA, delaying diagnosis. It underscores the importance of early bedside echocardiography and consideration of autoimmune etiologies in patients with unexplained pericardial effusions after common causes have been excluded, as prompt recognition and immunosuppressive therapy can be lifesaving.