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.