Steele’s disease is originally a juvenile form of arthritis with a systemic origin, but a similar disease can also occur in adults and is called Adult Steele’s disease (AOSD). The name “allergic subseptic disease” was once used. It is characterized by fever, arthralgia and/or arthritis, rash, myalgia, sore throat, enlarged lymph nodes, leukocytosis and neutrophilia, and thrombocytosis, with severe systemic damage. Because there are no specific diagnostic criteria, the diagnosis is often considered only after excluding infections, tumors and other connective tissue diseases. In some patients, even if the diagnosis of adult Still’s disease is made, close follow-up during treatment is required to further exclude these diseases. The prevalence of the disease is similar in men and women and is scattered worldwide without geographical differences. The age of onset is between 16 and 35 years, but it can also be seen at advanced ages.