Adult Still's disease is a rare illness marked by high, spiky 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.

• 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.
• 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.

Additional symptoms include:

• Swollen lymph nodes (glands)
• Sore throat
• Pain with a deep breath (pleurisy)
• Abdominal pain and swelling
• 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 that may suggest pericarditis or pleurisy.

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

• ESR (sedimentation rate) will be higher than normal
• CBC may show a high number of white blood cells and reduced number of red blood cells
• Liver function tests will show high levels of high AST /ALT
• Fibrinogen level will be high
• Ferritin (protein that stores iron) level will be very high
• Rheumatoid factor and ANA test will be negative

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

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