Adult-onset Still disease (AOSD) is a rare multisystem inflammatory disorder and was originally thought to be a variant of Still disease, a pediatric arthropathy.
On this page:
Epidemiology
Still disease in adults is rare affecting around 1.5 per 100,000 people, it occurs in a bimodal distribution with one peak around the age of 15-25 years old and another around the age of 35-45 years old 1. It affects females more than males 2.
Clinical presentation
Adult-onset Still disease classically is described as a triad of:
-
occasional non-infective cause of pyrexia of unknown origin 9
arthralgia
salmon-colored rash
Less common are:
sore throat
hepatic dysfunction
Elevated inflammatory markers (e.g. CRP), leukocytosis, thrombocytosis and elevated ferritin more than 1000 (an acute phase protein) are common 3,10.
Pathology
The cause of adult-onset Still disease is unknown but genetic, environmental and infectious factors may play a role 3,4. Elevated levels of various cytokines are seen in adult-onset Still disease. Interleukin-18-induced activation of macrophages and neutrophils appears to be important in Still disease. Interleukin-1-β also seems to be important in Still disease causing neutrophil production and diapedesis 5.
Diagnostic criteria
The Yamaguchi criteria is probably the most commonly used and sensitive scoring system for diagnosing adult-onset Still disease 6.
Markers
Adult-onset Still disease is a seronegative disease meaning a negative rheumatoid factor and antinuclear antibodies are commonly found.
Radiographic features
Plain radiograph
Pericapitate and trapezoid-metacarpal joint space narrowing without radiocarpal involvement is characteristic 7. This pattern is rarer in rheumatoid arthritis.
Treatment and prognosis
Steroids are commonly used to achieve remission of acute disease. Disease modifying antirheumatic drugs (DMARDs) may be used to maintain remission 3.
Three main patterns of disease have been described:
single acute episode before a period of lifelong remission
acute symptomatic episodes separated by months-years of no symptoms
chronic articular disease causing joint destruction 3
History and etymology
Adult-onset Still disease was described first in 1971, by the renowned British rheumatologist Eric George Lapthorne Bywaters (1910-2003) 8, who thought the disease resembled the systemic form of juvenile idiopathic arthritis a.k.a. Still disease 1.