Axial spondyloarthritis

Axial Spondyloarthritis (AxSpA) is a chronic, inflammatory rheumatic disease primarily affecting the spine and sacroiliac joints, leading to severe pain and stiffness in the axial skeleton. It falls under the broader category of Spondyloarthritis (SpA), which also includes peripheral spondyloarthritis. AxSpA is further subdivided into two main forms: radiographic AxSpA (also known as Ankylosing Spondylitis (AS)) and non-radiographic axial spondyloarthritis (nr-AxSpA).

Etiology and Pathogenesis

The exact cause of Axial Spondyloarthritis is unknown, but it is believed to involve a combination of genetic, immunological, and environmental factors. The most significant genetic risk factor is the presence of the HLA-B27 gene, although not everyone with the gene develops the condition. The disease process involves inflammation of the entheses (sites where ligaments and tendons attach to bone), leading to pain and potentially the formation of new bone, which can cause sections of the spine to fuse together.

Clinical Features

Patients with AxSpA typically experience chronic lower back pain and stiffness that improves with exercise but not with rest. This pain is often worse in the second half of the night and in the morning. Other symptoms may include fatigue, weight loss, and fever. Over time, the disease can lead to a reduction in spinal mobility and posture changes. Extra-articular manifestations such as Uveitis, Psoriasis, and Inflammatory Bowel Disease (IBD) can also occur.

Diagnosis

The diagnosis of Axial Spondyloarthritis is primarily based on clinical evaluation, imaging findings, and the presence of HLA-B27. Magnetic Resonance Imaging (MRI) is particularly useful in detecting early signs of inflammation in the sacroiliac joints and spine before they are visible on X-rays. The Assessment of SpondyloArthritis international Society (ASAS) criteria can help differentiate AxSpA from other causes of back pain.

Treatment

There is no cure for AxSpA, but treatment aims to relieve pain, reduce inflammation, maintain spinal mobility, and prevent or delay spinal damage. Nonsteroidal anti-inflammatory drugs (NSAIDs) are often the first line of treatment. Physical therapy and regular exercise are also crucial in managing symptoms and maintaining function. In cases where NSAIDs are ineffective, biologic medications, such as TNF inhibitors or IL-17 inhibitors, may be prescribed.

Prognosis

The prognosis for individuals with Axial Spondyloarthritis varies. Early diagnosis and treatment can significantly improve quality of life and potentially slow the progression of the disease. However, some individuals may experience progressive spinal fusion, leading to decreased mobility and function.

Epidemiology

AxSpA affects men and women, with a slightly higher prevalence in men. The onset of symptoms typically occurs in early adulthood. The prevalence of AxSpA varies globally, with estimates suggesting it affects about 0.1% to 1.4% of the population.