Adult-onset Still's Disease Presenting with Prolonged Fever, Polyarthralgia, and Hyperferritinemia: A Case Report.

Adult-onset still's disease (AOSD) is a rare systemic inflammatory disorder characterized by quotidian fever, inflammatory arthritis, rash, and markedly elevated serum ferritin levels. Due to its nonspecific presentation and the need to exclude infectious, autoimmune, and malignant etiologies, diagnosis remains challenging. We report a case of a middle-aged patient presenting with prolonged high-grade fever, diffuse abdominal pain, polyarthralgia, and generalized pruritus. Extensive investigations ruled out infectious and autoimmune causes. Markedly elevated inflammatory markers and hyperferritinemia supported the diagnosis of AOSD. The patient showed significant clinical improvement with corticosteroids and methotrexate therapy. This case highlights the importance of considering AOSD in patients with fever of unknown origin and hyperferritinemia after exclusion of other causes.