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

Abstract

Adult-Onset Still’s Disease (AOSD) is a rare systemic inflammatory disorder that is now considered part of the same disease spectrum as Systemic Juvenile Idiopathic Arthritis, sharing similar clinical and immunological features. It typically presents with a characteristic triad of high-grade fever, polyarthritis, and an evanescent salmon-colored maculopapular rash, along with systemic manifestations such as hepatosplenomegaly and lymphadenopathy. The pathogenesis involves dysregulated innate immunity with increased production of proinflammatory cytokines, particularly interleukin-1 and interleukin6. Diagnosis remains challenging due to its nonspecific presentation and overlap with infections, malignancies, and autoimmune diseases such as Systemic Lupus Erythematosus. The Yamaguchi criteria is the most widely used diagnostic tool, relying on clinical features and exclusion of alternative diagnoses. A 16-year-old male presented with a twomonth history of intermittent high-grade fever, accompanied by symmetric polyarthritis involving both large and small joints and an evanescent, non-pruritic salmon-colored rash predominantly affecting the trunk and extremities. Clinical examination revealed splenomegaly, tender and swollen metacarpophalangeal joints, and an otherwise stable systemic examination, although fundoscopy demonstrated Roth spots. Laboratory evaluation showed marked leukocytosis with neutrophilia, significantly elevated inflammatory markers including ESR and CRP, hyperferritinemia, and microcytic hypochromic anemia. Extensive investigations were performed to exclude differential diagnoses; blood cultures were negative, autoantibodies including ANA, RF, anti-CCP, and anti-dsDNA were absent, bone marrow examination excluded hematological malignancy, and echocardiography showed no evidence of infective endocarditis. Based on the fulfillment of the Yamaguchi criteria, a diagnosis of AOSD was established. The patient was initially treated with high-dose oral prednisolone and nonsteroidal anti-inflammatory drugs, followed by the addition of methotrexate due to partial response. Gradual tapering of corticosteroids was undertaken, and with continued immunosuppressive therapy, the patient achieved complete clinical remission with resolution of fever, arthritis, and rash. This case highlights the diagnostic complexity of AOSD in adolescents, a group in which the disease is infrequently recognized despite its overlap with Systemic Juvenile Idiopathic Arthritis. The presence of persistent fever, polyarthritis, characteristic rash, and elevated inflammatory markers should prompt consideration of AOSD after careful exclusion of infections, malignancies, and autoimmune conditions. Early diagnosis using the Yamaguchi criteria and timely initiation of corticosteroids and disease-modifying therapy are crucial for achieving remission and preventing complications. This case underscores the importance of increasing clinical awareness of AOSD in younger populations and supports the concept of a unified disease spectrum with sJIA, while emphasizing the need for improved diagnostic and therapeutic strategies.

Bangladesh J Medicine  2026; Vol. 37, No. 2(1): pp. 243-244