What Is Adult-Onset Still’s Disease?

Adult-onset Still’s disease (AOSD) is a rare type of autoinflammatory arthritis. An autoinflammatory condition occurs when the body’s immune system, which creates inflammation, does not work properly. In people with AOSD, the immune system is overactive and causes damage to the body. Most of the damage occurs in the joints.^1-4

Who gets AOSD?

Still’s disease is another name for systemic juvenile idiopathic arthritis (SJIA). It is a type of arthritis that kids get. When a person is diagnosed with Still’s disease after the age of 16 years old, it is considered "adult-onset" and called AOSD.⁵

Most people with AOSD are between the ages of 16 and 35, but adults of any age can be affected. All genders are thought to be affected equally.^1,2,5

What causes AOSD?

There is no known cause of AOSD. Some experts think an infection triggers the change in the immune system. These may be viral infections or bacterial infections. Certain genes or genetic factors may also increase a person’s risk for AOSD. Exposures in the environment may play a role too.^1,2,5

What are the symptoms of AOSD?

Although each person’s symptoms will be different, there are some common ones. They include:^1-5

• Recurring fevers, often daily in the afternoons or evenings
• Joint or muscle pain, especially in the knees and wrists
• Tiredness or fatigue
• Salmon-pink rash on the abdomen (trunk), arms, and legs
• Sore throat and swollen lymph nodes around the neck

About 1 in 3 people will have short-lived symptoms that resolve on their own. Another 1 in 3 will have occasional flare-ups of symptoms over time with no symptoms in between. The final 1 in 3 will have continuous, longer-term issues.^1-5

These symptoms can occur all at once, only during fevers, or at any time in between. Early treatment can help with reducing symptoms and flare-ups over time.^1-5

How is AOSD diagnosed?

Some of the symptoms of AOSD are nonspecific, like fevers, fatigue, joint pain, or rash. This means that they are common to many different health issues. For this reason, it can be challenging to diagnose AOSD.^2,5,6

There is no one specific test that can diagnose AOSD. Instead, your doctor will rule out other conditions first. They may look for:^2,5,6

• Infections
• Autoimmune conditions such as rheumatoid arthritis
• Certain cancers, like lymphoma

In order to rule out some of these other issues, your doctor will take a good history of your symptoms and other health conditions. They will also do a physical exam.^2,5

Blood tests may be helpful too. These include tests that look at blood cell counts (CBCs), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR). These tests look for signs of inflammation.^2,5

In some cases, you may undergo X-rays, magnetic resonance imaging (MRI), or other body images. These can help look for signs of joint damage or other injuries.^1,2

How is AOSD treated?

People with AOSD often make higher-than-normal levels of certain cytokines. Cytokines are proteins that play a role in the immune system. Many cytokines cause inflammation. This inflammation is what leads to joint damage.^4,7

Each person’s exact AOSD treatment plan will look different. However, most AOSD treatment options try to turn down the immune system response. Several common drugs used to treat AOSD are:^2,6,7

• Nonsteroidal anti-inflammatory drugs (NSAIDs) – These are used in mild cases of AOSD. Examples of over-the-counter NSAIDs are ibuprofen, aspirin, or naproxen. Some stronger NSAIDs are prescribed by a doctor.
• Steroids – Steroids affect the immune system as a whole and have many wide-reaching effects. Common steroids used for AOSD are prednisone or prednisolone. These drugs turn down the immune system quickly. However, they can have many side effects, especially when used over a long time.
• Disease-modifying antirheumatic drugs (DMARDs) – These drugs also have wide-reaching effects and many side effects. They are often used when NSAIDs or steroids are not controlling symptoms.
• Biologics – Biologics are a newer type of drug that is made from living cells. Biologics have specific targets in the body. For example, someone with AOSD may make too much of a cytokine called IL-6. There are biologic drugs that target that specific cytokine rather than the whole immune system.

Eating a balanced diet, exercising, and having strong mental and emotional health support are also important aspects of AOSD treatment. Your doctor can help create a well-rounded treatment plan for you.^2,6

What are the complications of AOSD?

Over time, AOSD can cause other health problems to arise. These are called complications, and they may include:^2-5

• Damage and destruction to the joints that make it hard to complete daily tasks
• Fluid around the lungs that makes it hard to breathe (pleural effusion)
• Lung inflammation or scarring (interstitial lung disease)
• Inflammation around the heart (pericarditis or myocarditis)
• Macrophage activation syndrome (MAS), a problem with the immune system that can be life-threatening

Each person’s experience with AOSD will be unique. Checking in with your healthcare team and taking treatments as prescribed can help with managing the condition.