Ankylosing spondylitis

Ankylosing spondylitis is a type of arthritis that affects the major bones of the skeleton, particularly the spine, although it can also affect peripheral joints as well. It is chronic, incurable and slow-progressing. Although it has a clear genetic component, there appears to be other factors in its development. While once thought to occur mostly in men, new studies show an occurrence of 2:1 between men and women. If untreated, it can result in all the bones of the spine becoming fused and totally inflexible. 
The disease was distinguished from rheumatoid arthritis in ancient times, and in several cases, appears in medical literature in the 16th century. However, the disease was not fully described until the late 19th century. 
One of the reasons the condition is difficult to diagnose is because it progresses very slowly, and it's initial symptoms are usually due to routine conditions like back strain. Onset is usually in a person's early 20's and take 8–11 years to develop into a debilitating condition. The earlier the disease presents, the more likely it is that it will affect other major joints as well. By the time the disease shows up on X-rays, it has usually progressed to a serious state. Other forms of radiology, like an MRI, show the disease in its early stages, but this is rarely used for the type of early symptoms typical of the disease. A definitive diagnosis is difficult, and usually combines clinical and radiological examination together with tests for genetic markers.
Because the disease is incurable, treatment focuses on lessening symptoms. Physiotherapy and exercise are important as symptoms are usually at their worst when the patient is at rest. Non-steroidal anti-inflammatories, such as ibuprofen, are used to reduce pain and inflammation. Narcotics may have to be used in severe cases, and steroids and chemotherapy can also be used to control the immune response that causes the disease. Surgery can be used for joint replacement, but it is not recommended for improving deformities of the spine due to the risk involved. 
Ankylosing spondylitis at NIH
Ankylosing spondylitis at Wikipedia
Ankylosing Spondylitis at Mayo Clinic
Ankylosing Spondylitis at CareDash
Ankylosing spondylitis