Beyond the Norm: A Unique Case of Adult-Onset Still's Disease.

Polyserositis, characterized by inflammation of multiple serous membranes, frequently occurs secondary to infection, malignancy, or rheumatological disorders. Adult-onset Still's disease (AOSD) is often diagnosed by exclusion, with the Yamaguchi criteria being essential for diagnosis. Disease severity is likely due to immune system changes, comorbidities, delayed diagnosis, and a higher risk of complications, necessitating more aggressive and carefully monitored treatments. We report the case of an elderly male who was diagnosed with AOSD by exclusion using the Yamaguchi criteria. The patient presented with bilateral pleural effusion, systemic inflammation, arthralgia, and fever. Initial investigations included complete blood count, C-reactive protein, and erythrocyte sedimentation rate, which revealed a severe acute phase reactant. Imaging studies, including chest X-ray and CT scan, revealed bilateral pleural effusion. Despite traditional treatment approaches, such as high doses of steroids and other immunosuppression medications, the patient's condition remained refractory, indicating the complex and challenging nature of managing AOSD in elderly patients. The increased severity and higher complication rates in older individuals require a multidisciplinary approach to ensure optimal outcomes. Aggressive treatment strategies, vigilant monitoring, and thorough diagnostic workups are essential to manage the disease effectively. This case highlights the need for heightened awareness and consideration of elderly onset Still's disease (EOSD) in differential diagnoses for elderly patients presenting with polyserositis and systemic inflammatory symptoms.