[Adult-onset Still's disease and its characteristic rash]

Still's disease was originally described as one form of rheumatoid arthritis in children beginning with fever and other systemic symptoms. In rare cases it may also begin in the adult and is then referred to as adult-onset Still's disease. The diagnostic criteria include typical rash, arthralgias, bouts of fever, and leukocytosis, as well as lymphadenopathy or splenomegaly, liver dysfunctions, noninfectious angina, and absence of rheumatoid factor and antinuclear antibodies. We report two adult patients with longstanding disease whose exanthema guided us to the correct diagnosis. The rash is a finding with high sensitivity. It is characterized by red macules with distinct borders and is evanescent. During an acute flare of the rash, gentle friction induces erythematous, isomorphic (Koebner) phenomena, which, as we describe here for the first time, may persist longer than the remainder of the fleeting rash.