A 35-year-old man presents with a 2-week history of high spiking fevers (up to 39.5 degrees C) each evening that resolves by morning, evanescent salmon-colored macular rash on the trunk during fevers, and polyarthralgia. Labs show ferritin 4200 ng/mL, WBC 18,000/mm3, ALT 88 U/L, and ESR 85 mm/hr. ANA and rheumatoid factor are negative. Blood cultures are sterile. Which of the following is the most likely diagnosis?
- A Adult-onset Still disease ✓
- B Acute myeloid leukemia
- C Disseminated tuberculosis
- D Systemic lupus erythematosus
Correct answer: A. Adult-onset Still disease
Explanation
Adult-onset Still disease classically presents with quotidian (daily) high fevers, evanescent salmon-pink rash, arthralgia/arthritis, and markedly elevated ferritin (often >1000). The Yamaguchi criteria require excluding malignancy, infection, and other rheumatic diseases. Negative ANA and RF support the diagnosis. Leukocytosis and transaminitis are common. Extremely elevated ferritin with glycosylated ferritin fraction below 20% is characteristic.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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