Abstract
Adult-onset Still's disease (AOSD) is a rare autoinflammatory disorder typified by quotidian fevers, an evanescent salmon-colored rash, arthralgia, neutrophilic leukocytosis, and markedly elevated inflammatory markers. Diagnosis is clinical and by exclusion, supported by classification frameworks like the Yamaguchi criteria. A previously healthy lady in her 20s presented with fever above 39°C, severe generalized myalgia, pharyngitis, a transient salmon-colored rash, neutrophilic leukocytosis, and markedly elevated inflammatory markers. Competing infectious, autoimmune, and malignant etiologies were excluded. Based on clinical features and Yamaguchi criteria, AOSD was suspected. She improved rapidly with intravenous methylprednisolone pulse therapy. During steroid taper as an outpatient, she developed a biochemical flare with ferritin rising to 8,807 ng/ml; tocilizumab was initiated for disease control. This case underscores prompt recognition of AOSD after exclusion of mimics, the interpretive value of ferritin trends, and successful escalation to interleukin-6 (IL-6) blockade for relapse, consistent with emerging data emphasizing targeted cytokine inhibition.