Adult Still's disease is a rare illness marked by high fevers, rash, and joint pain. It may lead to long-term (chronic) arthritis.

It is more commonly called adult-onset Still's disease (AOSD).

Fewer than 1 out of 100,000 people develop adult Still's disease each year. It affects women more often than men.

Still's disease that occurs in children is called systemic juvenile idiopathic arthritis.

The cause of adult Still's disease is unknown. No risk factors for the disease have been identified.

Almost all patients will have fever, joint pain, sore throat, and a rash.

• Joint pain, warmth, and swelling are common. Usually, several joints are involved at the same time. Often, patients have morning stiffness of joints that lasts for several hours.
• The fever usually comes on quickly once per day, most commonly in the afternoon or evening.
• The skin rash is typically salmon pink colored and comes and goes with the fever.

Additional symptoms include:

• Abdominal pain and swelling
• Pain with a deep breath (pleurisy)
• Sore throat
• Swollen lymph nodes (glands)
• Weight loss

Occasionally, the spleen or liver may become swollen. Lung and heart inflammation may occur.

Adult Still's disease can only be diagnosed after other diseases are ruled out. You may need many medical tests before a final diagnosis is made.

A physical exam may reveal a fever, rash, and arthritis. The health care provider will use a stethoscope to listen for changes in the sound of the heart or lungs.

The following blood tests can be helpful in diagnosing adult Still's Disease.

• Complete blood count (CBC) may show a high number of white blood cells and reduced number of red blood cells.
• C reactive protein (CRP), a measure of inflammation, will be higher than normal.
• ESR (sedimentation rate), a measure of inflammation, will be higher than normal.
• Ferritin level will be very high.
• Fibrinogen level will be high.
• Liver function tests will show high levels of high AST and ALT.
• Rheumatoid factor and ANA test will be negative.

Other tests may be needed to check for inflammation of the joints, chest, liver, and spleen.

• Abdominal ultrasound
• CT scan of the abdomen
• X-rays of the joints, chest, or stomach area (abdomen)

The goal of treatment for adult Still's disease is to control the symptoms of arthritis. Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen are usually the first form of treatment.

Prednisone may be used for more severe cases.

If the disease persists for a long time (becomes chronic), medicines that suppress the immune system might be needed. Such medicines include:

• Methotrexate
• Tumor necrosis factor (TNF) antagonists such as Enbrel (etanercept)

Studies show that in about 20% of patients, all symptoms go away in a year and never come back. In about 30% of patients, all symptoms go away but then come back several times over the next years.

Symptoms continue for a long-time (chronic) in about half of patients with adult Still's disease.

• Arthritis in several joints
• Liver disease
• Pericarditis
• Pleural effusion
• Spleen enlargement

Call your health care provider if you have symptoms of Adult Still's disease.

If you have already been diagnosed with the condition, you should call your health care provider if you have a cough or difficulty breathing.

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Pay S, Turkcapar N, Kalyoncu M, et al. A multicenter study of patients with adult-onset Still's disease compared with systemic juvenile idiopathic arthritis. Clin Rheumatol. 2005 Dec 20;:1-6.

Efthimiou P, Paik PK, Bielory L. Diagnosis and management of adult onset Still's disease. Ann Rheum Dis. 2006 May;65(5):564-72. Epub 2005 Oct 11. Review.

Kadar J, Petrovicz E. Adult-onset Still's disease. Best Pract Res Clin Rheumatol. 2004 Oct;18(5):663-76. Review.