BACKGROUND: Adult Still’s disease (ASD) is a rare systemic inflammatory condition, which commonly presents with the triad of quotidian fevers, rash, and non-specific rheumatologic symptoms such as myalgia and arthralgia. The etiology and pathogenesis are poorly understood and both the clinical presentation and laboratory data are typically nonspecific. As such, the presentation is often confused with infection, other autoimmune processes, and malignancy.

CASE REPORT: We present a case of a 29-year-old Hispanic female who presented with fever, sore throat, myalgia, and shortness of breath. Initially diagnosed with suspected pneumonia, extensive workup led to the final diagnosis of ASD due to the persistence of her symptoms, which met Yamaguchi Criteria, as well as exclusion of other possible etiologies.

CONCLUSIONS: ASD is a rare systemic inflammatory condition and its nonspecific presentation often leads to diagnostic delay and disease complications. We discuss the incidence, etiology, pathology, diagnosis, and standards in management of ASD. This case emphasizes the need for high clinical suspicion of ASD, and early exclusion of other etiologies, especially with failure of first-line treatment, to limit patient suffering and complications.

Keywords: Fever of Unknown Origin, Rheumatology, Still's Disease, Adult-Onset