Challenging diagnosis of adult-onset still's disease (AOSD) in a young male: a case report highlighting the importance of early recognition and management.

Introduction and Importance: Adult-Onset Still's Disease (AOSD) is a rare systemic inflammatory disorder that poses significant diagnostic challenges, particularly in younger patients. This case report details the diagnosis and management of AOSD in a 16-year-old male, emphasizing the critical need for early recognition to optimize patient outcomes and improve quality of life. Case Presentation: A 16-year-old male presented with a 2-month history of high-grade intermittent fever, symmetric polyarthritis, and an evanescent salmon-colored maculopapular rash. Laboratory investigations revealed microcytic hypochromic anemia, neutrophilic leukocytosis, thrombocytosis, elevated inflammatory markers (ESR, CRP, ferritin), and negative autoantibodies. The patient fulfilled all Yamaguchi criteria for AOSD. Initial treatment with corticosteroids and nonsteroidal anti-inflammatory drugs (NSAIDs) showed limited response, but the addition of methotrexate resulted in near complete symptom resolution. Clinical Discussion: Diagnosing AOSD in a young male is complex due to its overlapping features with infectious, hematological, and autoimmune conditions. This case underscores the importance of considering AOSD in adolescents presenting with characteristic symptoms and highlights the efficacy of methotrexate as a steroid-sparing agent in achieving disease control. Conclusion: Early diagnosis and tailored therapeutic interventions are essential for effective AOSD management, particularly in younger populations. This case emphasizes the need to include AOSD in the differential diagnosis of fever, rash, and arthritis to prevent diagnostic delays and ensure favorable outcomes.