Adult-onset Still’s disease – AOSD: Causes, Diagnosis and Treatment

by Johnny Jacks

Adult-onset Still’s disease (AOSD) is a rare inflammatory disorder that can affect the entire body. The cause of the disease is unknown (idiopathic). AOSD has three typical characteristic symptoms, including spiking fevers, joint pain or inflammation, and skin rash, which appear in 75-95% of patients.

What is Adult-onset Still’s Disease?

Adult-onset Still’s Disease (AOSD) is a rare systemic inflammatory disorder characterized by daily spiking fevers, polyarthritis, and fleeting skin rash. AOSD is also called systemic-onset idiopathic arthritis.

AOSD is a very rare disease, with an estimated annual incidence rate of 0.1 to 0.4 cases per 100,000 individuals. Based on larger evaluations since the 1980s, it appears to occur worldwide and affects females slightly more frequently than males. The disease is characterized by affecting young individuals, with 3/4 of patients reporting onset between 16 and 35 years of age.

What is Adult-onset Still's Disease?

What is Adult-onset Still’s Disease?

Causes of Adult-onset Still’s Disease

The etiology of AOSD, like most inflammatory arthropathies, is still not well understood. The hypothesis is still that AOSD is a reactive syndrome, in which various infectious agents may act as disease triggers in genetically susceptible hosts.

Both genetic factors and certain viruses, bacteria such as Yersinia enterocolitica and Mycoplasma pneumoniae, and other infectious agents may be causative factors.

Furthermore, in a study, an association of AOSD with certain HLA antigen subgroups has been found.

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The clinical symptoms of adult-onset Still’s disease

AOSD has three typical characteristic symptoms including high fever with a peak, joint pain or inflammation, and skin rash. These symptoms appear in 75-95% of patients. Other common symptoms are muscle pain, sore throat, enlarged lymph nodes and spleen. In addition, there are rare symptoms such as hepatomegaly, pleurisy, pericarditis, and abdominal pain.

Patients with AOSD usually have high fever over 39°C and last for at least 4 hours. Fever recurs daily or every other day, especially in the evening and early morning, and the patient’s body temperature returns to normal between fever episodes. High fever often appears before other symptoms such as pharyngitis, sore throat, muscle pain, and joint pain.

The rash in these patients is usually salmon-colored, with yellow or golden spots that are not itchy and occur during fever, disappearing when the fever subsides. These rash nodules are mainly seen on the back and extremities, but can also be seen on the palms, soles of the feet, and face. The rash may sometimes be caused by the patient taking a hot bath or rubbing the skin, known as the Koebner phenomenon.

About 64-100% of AOSD patients experience joint pain or inflammation. Initial joint inflammation may be mild, fleeting, and affect a few joints, but it can progress to serious, destructive, and symmetrical polyarthritis. Common joints affected are the knees, wrists, and ankles. Alternatively, it may also affect the elbow, intercostal joint, shoulder, carpal bones, tarsal bones, hip, and temporomandibular joint. In some AOSD patients, there is a characteristic involvement of the wrist joints. In AOSD patients, inflamed joints usually do not become deformed or fused, but joint inflammation progresses with high fever and may lead to knee joint effusion.

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In addition, AOSD patients may experience more severe muscle pain when fever spikes, sometimes leading to serious weakness and debilitation.

Signs of Still's disease in adults

Signs of Still’s disease in adults

How is Still’s disease diagnosed in adults?

Through clinical and laboratory findings, there are several criteria for diagnosing adult-onset Still’s disease (AOSD), among which the Yamaguchi criteria from Japan are the most sensitive and widely used.

Patients with five or more criteria, including at least two major criteria, with a sensitivity of 96% and a specificity of 92%, are diagnosed with AOSD.

The major criteria are as follows:

  • Fever lasting at least 1 week, with a temperature of 39°C or higher
  • Arthralgia or arthritis for at least 2 weeks
  • Salmon-colored rash on the trunk or limbs
  • Leukocytosis with neutrophilia (10,000/µL or higher)

The minor criteria for diagnosing AOSD are:

  • Sore throat
  • Lymphadenopathy
  • Hepatomegaly or splenomegaly
  • Abnormal liver function tests
  • Negative tests for RF and ANA

Clinical presentations of AOSD are divided into three types based on the clinical manifestations:

  • Self-limiting or mild AOSD is characterized by systemic symptoms such as fever, rash, pharyngitis, and organ involvement. Most patients have a spontaneous remission within one year (average time is 9 months) after the first and only episode.
  • Intermediate or subacute AOSD is characterized by relapsing and remitting episodes with or without joint involvement. There is complete remission between episodes, which may be several years apart, and is milder than the initial presentation.
  • Chronic articular AOSD is characterized by severe joint involvement leading to joint destruction. Patients with predominantly articular symptoms, chronic polyarthritis, may lead to joint damage. Among these patients, 67% require joint replacement at least once, on average, 28 months (range, 13 to 60 months) after disease onset.
How is Still's disease diagnosed in adults?

How is Still’s disease diagnosed in adults?

How is adult Still’s disease treated?

The treatment of AOSD focuses on the use of NSAIDs, steroids, and disease-modifying anti-rheumatic drugs (DMARDs) to control fever, joint inflammation, and systemic symptoms.

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NSAID monotherapy is effective in controlling the disease in only 15% of patients with joint inflammation symptoms.

Between 76% and 95% of patients treated with steroids respond, with a daily dose of corticosteroids ranging from 1 to 1.5 mg/kg, followed by tapering.

If AOSD patients do not respond well to corticosteroids, basic treatment drugs need to be combined. Initially, the patient is given methotrexate, and if there is still no response, cyclophosphamide is used. In addition, AOSD patients can be given cyclosporin A, hydroxychloroquine, D-penicillamine, azathioprine, and other drugs.

If patients do not improve after using the above treatments, gamma globulin infusion can be administered at a dose of 0.4-2 grams/kg per day for 2-5 days.

The above are the information on adult Still’s disease, hoping it will be useful for readers in the process of diagnosis and treatment of the disease.

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