Adult-onset Still disease is an idiopathic systemic disorder that presents with relapsing high fever, joint pain, skin rash, pharyngitis, hepatosplenomegaly, and lymphadenopathy. The diagnosis rests on clinical criteria and a thorough laboratory workup, with an emphasis on inflammatory markers and ferritin.
Adult-onset Still disease (AOSD), commonly referred in the literature as the adult form of systemic-onset juvenile idiopathic arthritis, is a disorder of unknown etiology  . The clinical presentation might be quite different from patient to patient, but the following manifestations are included in the diagnostic criteria    :
Other common manifestations of AOSD are lymphadenopathy, hepatosplenomegaly, muscle aches, and pharyngitis  . The clinical course of the disorder can be highly variable, ranging from mild and self-limiting to severely debilitating disease . Furthermore, AOSD may cause a myriad of complications in affected individuals, such as pulmonary hypertension, thrombotic thrombocytopenic purpura (TTP), amyloidosis, and macrophage activation syndrome . An early detection of this disorder could significantly aid in successful treatment and improvement of the overall quality of life.
The diagnosis of AOSD is primarily a one of exclusion, as numerous autoimmune, malignant, and infectious diseases induce the nonspecific signs and symptoms seen in this condition    . Thus, a comprehensive clinical and laboratory workup is necessary. Firstly, during a history taking, patients should be asked about the course of the disease and the appearance of symptoms, whereas a thorough physical examination has an important role in identifying lymphadenopathy, cutaneous changes, joint inflammation, and hepatosplenomegaly.
A complete blood count (CBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and serum ferritin should be evaluated in laboratory studies     . Additionally, rheumatoid factor (RF) and antinuclear antibodies (ANA), both performed to exclude conditions such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), are also recommended in the initial workup .
Current diagnostic criteria are divided into major (Fever ≥ 39°C, joint pain, skin rash, pharyngitis, granulocytosis of ≥ 80%, and glycosylated ferritin fraction of ≤ 20%) and minor (leukocytosis of > 10,000/mm3 and a typical skin rash)    . AOSD is confirmed if ≥ 4 major criteria or 3 major and 2 minor criteria are met    .