The axial skeleton refers to the backbone or spine (vertebrae, sacrum, and coccyx) along with the ribs and breastbone (sternum). Non-radiographic axial spondyloarthropathy is a term that describes a condition that produces predominantly axial spinal symptoms, mainly related to the sacroiliac and lower spine. This designation refers to people with clinical features of AS but with normal imaging studies of the sacroiliac joints and spine. AS is a chronic and multisystem inflammatory disorder that may involve any of the spine joints. X-rays of the spine can detect AS. Some researchers suggest that nr-axSpA represents either an incomplete form of AS or is a milder form of AS. Thus, the definition of nr-axSpA can be AS symptoms of the lower axial spine with no radiographic changes.
The cause or etiology of AS and nr-axSpA is unknown. Researchers suggest that a combination of genetic and environmental factors are likely risk factors. For example, people with HLA-B27 genes have an increased risk for the disease, and AS is more common in people with relatives with AS. An immune response to a bacterial infection such as Klebsiella may trigger AS, nr-axSpA, and other related AS diseases.
The main symptom of nr-axSpA is back pain (symptoms lasting 3 or more months) that is worse late at night or early morning. The pain typically begins slowly in the teen or young adult years, up to about age 40. Some patients may have mild pain and stiffness for years. Symptoms often improve after exercise. Uveitis (a form of eye inflammation) may develop in some individuals. The prevalence of nr-axSpA in people with inflammatory back pain is highest in Asia (36.46%) and lowest in Africa (16.02%).
Doctors, in general, diagnose nr-axSpA by two main criteria: chronic back pain (clinical symptoms, tendon swelling) and the absence of clear radiographic changes in the axial spine. There are several published criteria for an AS back pain diagnosis that some doctors may also use. MRI may reveal early axial joint changes not visible on X-rays. Rheumatologists are specialists who diagnose and treat AS diseases.
Treatment usually includes pain medication and exercise programs. Anti-inflammatory and immune-suppressive drugs may reduce symptoms. Cimzia (Certolizumab) was recently approved to treat nr-axSpA. Cosentyx (secukinumab) treats AS, and some doctors may use it to treat nr-axSpA. Some doctors may choose AS treatments like sulfasalazine, corticosteroids, or other medications.
The prognosis of nr-axSpA may vary from good to fair depending on the patient's response to treatments. If nr-axSpA advances further into AS, the prognosis worsens.
Pain in the lower back or low back pain is a common concern, affecting up to 80% of Americans at some point in their lifetime. Many will have more than one episode. Low back pain is not a specific disease, rather it is a symptom that may occur from a variety of different processes. In up to 85% of people with low back pain, despite a thorough medical examination, no specific cause of the pain can be identified.