[Fever of unknown origin caused by the adult form of Still's disease].

In three patients, two women aged 70 and 19 years and a man aged 33 years with long-lasting fever no diagnosis was made after extensive diagnostic work-up. After exclusion of infectious, malignant and rheumatic diseases, adult-onset Still's disease was diagnosed in all three patients on the basis of clinical and laboratory criteria. Adult-onset Still's disease is an important but less well known cause of fever. Clinically, adult-onset Still's disease is characterized by the triad of fever, skin rash and arthritis/arthralgia. A greatly elevated serum ferritin level proved to be an additional valuable diagnostic clue. Treatment consists of non-steroidal anti-inflammatory drugs, corticosteroids or immunosuppressive agents. The long-term prognosis is usually good, but severe joint destruction may occur. All three patients recovered.