Rheumatoid arthritis diagnostic pitfalls: don’t overlook large joint effusion - a case report

<p><strong>Background:</strong> Rheumatoid arthritis (RA) is a systemic autoimmune disease that commonly presents of inflammatory symmetric polyarthritis in small joints and may also have extra-articular involvement. Early diagnosis and treatment within the first 3 months are important to reduce progression and deformities. In some cases, large joint involvement may also present or initially present in RA, which may lead to lower suspicion of RA at the initial visit and results in delayed diagnosis.</p> <p><strong>Case Presentation:</strong> Here we present a case of female, 55 years old with knee joint pain and effusion, which initially thought to be osteoarthritis. The patient had inflammatory arthritis features including morning stiffness, pain worsened at rest, and arthritis also involving hands. Yet, the patient was confirmed as having rheumatoid arthritis based on clinical, serological, and radiological features. In the detailed evaluation of knee radiographic examination, bone erosions were identified at a second look.</p> <p><strong>Conclusion:</strong> Inflammatory arthritis involving large joints requires detailed history taking of other joint involvement, serologic evaluation and also thorough radiographic interpretation, thus diagnosis of rheumatoid arthritis involving large joint can be established properly.</p>