Case Presentation: A 19-year-old woman with a history of anxiety was admitted to the hospital with one week of fever to 103 degrees F, sore throat, fatigue, and severe arthralgias. History was notable for pleuritic chest pain, an intermittent rash over her arms and thighs, and a 23-pound weight loss over 12 months, which she attributed to lifestyle changes. On arrival she was afebrile with a heart rate of 150 beats per minute and normal oxygen saturation on ambient air. Exam revealed an ill appearing young woman with clear lung fields, no heart murmur or rub, and exquisite tenderness to palpation of all joints without synovitis or effusion. No rash was observed. She had returned from a backpacking trip to Colorado one-month prior and lived with two cats. Labs revealed WBC count 15.7 K/L with 82% neutrophils, hemoglobin 8.9 g/dL, CRP greater than 300 mg/L, ESR 120 mm/hr and ferritin 4,358 ug/L. EKG showed sinus tachycardia. Computed tomography (CT) angiogram revealed enlarged left axillary lymph nodes without pulmonary embolus and CT abdomen/pelvis revealed mild splenomegaly. She was covered broadly with antibiotics, including doxycycline for possible tick-borne diseases. She received intravenous fluids, antipyretics and analgesics for pain control without improvement in fever curve or symptoms. Persistence of tachycardia raised concern for myocarditis. High sensitivity troponin peaked at 44 ng/L and echocardiogram revealed normal systolic function. She declined a cardiac MRI. Extensive infectious work-up was negative and antibiotics were stopped. Her presentation of daily fever, arthralgias, rash, elevated acute phases reactants and myocarditis, in the absence of infection or malignancy, was felt to be diagnostic of adult-onset Still’s disease (AoSD). High dose steroids were started with significant improvement in symptoms and laboratory markers of inflammation. She was transitioned to oral steroids and was discharged home with close Rheumatology follow-up.

Discussion: AoSD is an inflammatory disorder that classically presents with daily fevers greater than 102 degrees F, arthralgias or arthritis and an evanescent rash. Labs are non-diagnostic but usually reveal leukocytosis with a predominance of granulocytes and elevated acute phase reactants. Rarely, myocarditis is a presenting feature as in this case. As the diagnosis of AoSD is one of exclusion, initial work-up should exclude infectious, malignant and other rheumatologic diseases that may present similarly.

Conclusions: AoSD is a rare inflammatory disease whose characteristic presentation of daily fevers, arthralgias or arthritis and an evanescent rash that can often be confused with infectious, malignant and rheumatologic disease processes. Hospitalists must be diligent in pursuing a full diagnostic evaluation prior to consideration of a diagnosis of AoSD.