Adult-onset Still’s Disease without Elevation of Erythrocyte Sedimentation Rate, C-reactive Protein or Serum Ferritin: A Case Report

Fever accompanied by arthralgia and rash has multiple differential diagnoses. It often resembles a viral exanthem and is treated accordingly. However, certain clinical and laboratory features may suggest a specific diagnosis. Here, authors present the case of a 19-year-old male who had fever, polyarthralgia, throat pain, and pinkish rashes. The rashes appeared with the onset of fever and resolved when the fever subsided. He was initially treated for a viral exanthem, with bacterial infection considered in the differential diagnosis. As he did not respond to standard fever management, proceeded to exclude specific infections, malignancy, and autoimmune conditions. After a thorough evaluation, he was diagnosed Adult-Onset Still’s Disease (AOSD), which responded well to oral corticosteroids. AOSD is an autoinflammatory disorder with systemic manifestations characterised by high spiking fevers, polyarthralgia, and a typical salmon-pink rash. The rash is usually non pruritic, macular or maculopapular, and often coincides with febrile episodes. It is one of the differential diagnoses in Pyrexia of Unknown Origin (PUO), warranting appropriate and comprehensive evaluation. Classically, AOSD demonstrates elevated inflammatory markers, particularly serum ferritin. Interestingly, index patient had normal values of all three inflammatory markers {Erythrocyte Sedimentation Rate (ESR), C-Reactive Protein (CRP), and serum ferritin} despite having an inflammatory disease, which makes this presentation rare in an already uncommon condition. This report indicates that AOSD can present without a typical rise in inflammatory markers, creating a diagnostic dilemma. Only strong clinical suspicion may lead to an accurate diagnosis.