Adult-onset Still's disease is an inflammatory disease that may affect many joints, internal organs, and other parts of the body. Adult Still's develops most often in people before age 45, but can first occur in later years as well. The cause of Still's is unknown and there are no known risk factors. It is thought that a virus or other type of infectious agent may trigger Still's disease, but there is no proof.
Although some features are similar, adult-onset Still's disease is different than Still's in children. In children, Still's disease is considered a form of juvenile rheumatoid arthritis and referred to as systemic-onset juvenile rheumatoid arthritis. Less than one in 100,000 people develop adult-onset Still's each year and it is more common in women.
There is no specific test to diagnose ankylosing spondylitis, but imaging by X-ray and MRI may show evidence of inflammation of the sacroiliac joint between the sacrum (the triangular bone at the lowest part of the back) and the ilium (the bone felt on the upper part of the hip). Some symptoms may include:
Inflammatory back pain (gradual in onset, lasting over three months, with stiffness and pain that is worse in the morning and improved with movement)
Reduced mobility of the spine
Common Symptoms of Adult-Onset Still's Disease (AOSD)
Almost all people with adult-onset Still's disease have fevers, joint pain, sore throat, and a rash. But the type, pattern, and severity of symptoms vary from person to person and even from month to month for the same person. For example, symptoms may come and go. And, at first you may have just a few symptoms, then later you may have more.
These are common symptoms of adult Still's disease:
A fever (equal to or greater than 102 degrees) that comes on quickly once per day, usually in the afternoon or evening. For most people, these fevers resolve without treatment.
Joint pain, warmth, and swelling affecting a few joints at first -- often knees and wrists -- then several joints. Morning joint stiffness often lasts for several hours.
A salmon pink-colored skin rash that usually comes and goes with the fever and usually doesn't itch. Flat spots or both flat spots and small, raised bumps may appear on your torso, upper arms or legs, or face.
Severe muscle aches, which also may ebb with the fever.
A sore throat that can be severe, constant, and burning.
Other symptoms of adult-onset Still's may include:
Contact your doctor if you experience any of the symptoms of adult-onset Still's disease. If you've already been diagnosed and have breathing troubles, call your doctor right away. In addition to lung, liver, or heart inflammation, complications of Still's may include chronic arthritis in several joints.
Diagnosis of Adult-Onset Still's Disease
It can be difficult to diagnose Still's disease. That's because Still's has some similarities to other diseases, such as Lyme disease, Crohn's disease, and certain infections. Before confirming your diagnosis, your doctor will need to rule out other problems.
A medical history and physical exam are often the first steps. You may need a variety of blood tests to check for inflammation, changes in blood cell counts, iron levels, and liver enzymes, for example. Imaging tests check for inflammation or enlargement of certain organs.