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 [1] [2]. The clinical presentation might be quite different from patient to patient, but the following manifestations are included in the diagnostic criteria [1] [3] [4] [5]:

• Fever - Although not specific, the recurring appearance of very high fever (> 39°C) that lasts for a few hours and mainly happens in the late afternoon or early evening period, is a hallmark of AOSD [3] [6].
• Joint pain - The involvement of knees, wrists, or ankles is another important manifestation of AOSD [3] [4]. Arthritis usually accompanies fever and has a relatively short duration as well [3].
• Rash - A salmon-pink or erythematous nonpruritic maculopapular rash, developing together with fever and joint pain, is frequently observed, and is most commonly seen on the trunk and the proximal limbs [5].

Other common manifestations of AOSD are lymphadenopathy, hepatosplenomegaly, muscle aches, and pharyngitis [1] [7]. The clinical course of the disorder can be highly variable, ranging from mild and self-limiting to severely debilitating disease [3]. Furthermore, AOSD may cause a myriad of complications in affected individuals, such as pulmonary hypertension, thrombotic thrombocytopenic purpura (TTP), amyloidosis, and macrophage activation syndrome [1]. 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 [1] [3] [7] [8]. 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 [1] [3] [4] [7] [8]. 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 [3].

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) [3] [4] [7] [8]. AOSD is confirmed if ≥ 4 major criteria or 3 major and 2 minor criteria are met [1] [3] [4] [7].

The treatment of Adult-Onset Still's Disease focuses on managing symptoms and controlling inflammation. Nonsteroidal anti-inflammatory drugs (NSAIDs) are often the first line of treatment to reduce fever and pain. Corticosteroids, such as prednisone, may be prescribed for more severe cases to suppress the immune response. In patients who do not respond to these treatments, disease-modifying antirheumatic drugs (DMARDs) or biologics, which target specific components of the immune system, may be used.

The prognosis for individuals with AOSD varies. Some patients experience a single episode that resolves with treatment, while others may have recurrent episodes or develop chronic disease. Long-term complications can include joint damage and organ involvement. Early diagnosis and appropriate treatment are crucial for improving outcomes and minimizing complications.

The exact cause of Adult-Onset Still's Disease is unknown. It is believed to result from a combination of genetic and environmental factors that trigger an abnormal immune response. Some researchers suggest that infections may play a role in triggering the disease, although no specific infectious agent has been identified.

Adult-Onset Still's Disease is a rare condition, with an estimated incidence of 1 to 34 cases per million people per year. It can occur at any age but is most commonly diagnosed in young adults between the ages of 16 and 35. The disease affects both men and women, although some studies suggest a slight female predominance.

The pathophysiology of AOSD involves dysregulation of the immune system, leading to excessive production of inflammatory cytokines, which are proteins that mediate inflammation. Key cytokines implicated in AOSD include interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha). This cytokine storm results in the systemic inflammation and symptoms observed in the disease.

Currently, there are no known methods to prevent Adult-Onset Still's Disease, as its exact cause remains unclear. Research is ongoing to better understand the disease's triggers and mechanisms, which may eventually lead to preventive strategies.

Adult-Onset Still's Disease is a rare inflammatory disorder characterized by high fevers, joint pain, and a distinctive rash. Diagnosis involves ruling out other conditions and identifying characteristic symptoms and laboratory findings. Treatment focuses on managing inflammation and symptoms, with a range of medications available depending on disease severity. While the cause of AOSD is not fully understood, ongoing research aims to uncover its underlying mechanisms and potential preventive measures.

If you or someone you know is experiencing symptoms such as high fevers, joint pain, and a salmon-colored rash, it is important to seek medical evaluation. Adult-Onset Still's Disease is a rare condition that requires careful diagnosis and management. Treatment options are available to help control symptoms and improve quality of life. Regular follow-up with a healthcare provider is essential to monitor the disease and adjust treatment as needed.

1. Kadavath S, Efthimiou P. Adult-onset Still's disease-pathogenesis, clinical manifestations, and new treatment options. Ann Med. 2015;47(1):6-14.
2. Gerfaud-Valentin M, Jamilloux Y, Iwaz J, Sève P. Adult-onset Still's disease. Autoimmun Rev. 2014;13(7):708-722.
3. Efthimiou P, Paik PK, Bielory L. Diagnosis and management of adult onset Still’s disease. Ann Rheum Dis. 2006;65(5):564-572.
4. Gopalarathinam R, Orlowsky E, Kesavalu R, Yelaminchili S. Adult Onset Still’s Disease: A Review on Diagnostic Workup and Treatment Options. Case Reports in Rheumatology. 2016;2016:6502373.
5. Mobini M, Ghasemian R, Zameni F. Adult Onset Still's Disease With Different Antibodies: A Case Report and Review of Literature. Acta Med Iran. 2016;54(10):683-685.
6. Larson EB. Adult Still's disease—recognition of a clinical syndrome and recent experience. West J Med. 1985;142:665–671.
7. Dudziec E, Pawlak-Buś K, Leszczyński P. Adult-onset Still’s disease as a mask of Hodgkin lymphoma. Reumatologia. 2015;53(2):106-110.
8. Meijvis SC, Endeman H, Geers AB, ter Borg EJ. Extremely high serum ferritin levels as diagnostic tool in adult-onset Still's disease. Neth J Med. 2007;65(6):212-214.