Ankylosing spondylitis - causes, symptoms, diagnosis, treatment, pathology

Summary

Ankylosing spondylitis, a chronic inflammatory disease, primarily affects the spine's vertebrae, causing stiffness and pain. It is part of the seronegative spondyloarthropathies, autoimmune disorders that do not show rheumatoid factor in the blood. The condition is associated with the HLA-B27 gene and can lead to joint inflammation, potentially causing systemic effects like eye inflammation and fatigue. Diagnosis involves MRI, X-ray, and genetic testing. Treatment options include NSAIDs, physical therapy, DMARDs, and biologics, with surgery being a last resort.

Takeaways

• 🔬 **Ankylosing Spondylitis Definition**: Ankylosing spondylitis is a chronic inflammatory disease affecting the vertebral joints, causing stiffness and potentially inflammation in other body parts.
• 🏃‍♂️ **Seronegative Spondyloarthropathies**: It is part of seronegative spondyloarthropathies, autoimmune diseases affecting joints without rheumatoid factor in the blood.
• 🦴 **Vertebral Column Structure**: The human vertebral column consists of cervical, thoracic, lumbar vertebrae, sacrum, and coccyx, with intervertebral discs and facet joints allowing movement and providing support.
• 🔄 **Joint Function**: Intervertebral discs and facet joints facilitate slight movement and act as shock absorbers, with facet joints also helping to guide and limit the spine's range of motion.
• 🚑 **Inflammation in AS**: Ankylosing spondylitis involves chronic inflammation of the inner vertebral and facet joints, with the exact cause being unclear but linked to autoimmune processes.
• 🧬 **HLA B27 Gene**: Most individuals with ankylosing spondylitis have the HLA B27 gene, which encodes for a specific type of MHC class 1 molecule, potentially involved in the disease's autoimmune response.
• 💉 **Immune System's Role**: The immune system, particularly CD8 positive T cells, may mistakenly target the body's own collagen due to the presentation of self-antigens by MHC class 1 molecules.
• 🛡️ **Progression and Effects**: Over time, inflammation can destroy joint structures, leading to replacement by fibrin and eventually bone through ossification, causing a 'bamboo spine' appearance on imaging.
• 🏥 **Diagnosis Methods**: Ankylosing spondylitis can be diagnosed using MRI, X-ray, and CT, with genetic testing for HLA B27 also being a confirmatory tool.
• 💊 **Treatment Options**: Treatment includes non-steroidal anti-inflammatory drugs, exercise, physical therapy, disease-modifying anti-rheumatic drugs, and biologics that target cytokines.

Q & A

What does the term 'ankylosing spondylitis' mean?

Ankylosing spondylitis refers to a chronic inflammatory disease that affects the vertebral joints, causing the spine to become stiff. The term 'ankylosing' means stiffening, 'spondylo' refers to the vertebra, and 'itis' refers to inflammation.

What is the difference between seronegative and seropositive spondyloarthropathies?

Seronegative spondyloarthropathies, like ankylosing spondylitis, are autoimmune diseases that affect the joints and are characterized by the absence of rheumatoid factor in the blood. In contrast, seropositive conditions have a presence of rheumatoid factor.

How many bones make up the vertebral column in a healthy adult?

In a healthy adult, the vertebral column is composed of 33 bones: 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, the sacrum, and the coccyx.

What are the two types of joints between the vertebrae?

There are two types of joints between the vertebrae: intervertebral discs, which allow slight movement and act as shock absorbers, and facet joints, which guide and limit the range of motion in the spine.

What is the role of the major histocompatibility complex (MHC) in ankylosing spondylitis?

The MHC class 1 molecules, particularly those encoded by the HLA-B27 gene, present molecules from within the cell for the immune system to sample. In ankylosing spondylitis, this process can lead to the immune system mistakenly attacking the body's own tissues, such as the collagen in the joints.

What is the significance of the HLA-B27 gene in ankylosing spondylitis?

Most individuals with ankylosing spondylitis have the HLA-B27 gene, which encodes for a specific type of MHC class 1 molecule. This gene is associated with the autoimmune process that attacks vertebral joints.

How does the immune system's response to self-antigens contribute to ankylosing spondylitis?

In ankylosing spondylitis, the immune system may mistakenly recognize self-antigens, such as type 1 and type 2 collagen in the joints, as foreign. This leads to an autoimmune response, causing inflammation and damage to the joints.

What is the process by which the spine becomes stiff and immobile in ankylosing spondylitis?

In ankylosing spondylitis, chronic inflammation destroys the inner vertebral joints and facet joints. Fibroblasts replace the destroyed joint with fibrin, and eventually, osteoblasts activate, leading to ossification and the formation of a bamboo spine, which immobilizes the affected parts of the spine.

What are some of the extra-spinal manifestations of ankylosing spondylitis?

Ankylosing spondylitis can affect other parts of the body, including the eyes (causing anterior uveitis), the aortic valve (leading to aortic regurgitation), tendons (causing enthesitis), and the lungs (causing shortness of breath due to stiffness).

How is ankylosing spondylitis diagnosed?

Ankylosing spondylitis can be diagnosed using MRI, which shows erosion and narrowing of joint spaces early on and joint fusion later on. X-rays and CT scans may reveal a bamboo spine appearance, and genetic testing for HLA-B27 can help confirm the diagnosis.

What are the common treatments for ankylosing spondylitis?

Treatment for ankylosing spondylitis includes non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, exercise or physical therapy, and in more severe cases, disease-modifying anti-rheumatic drugs (DMARDs) or biologics that block cytokines. Surgery may be considered for damaged hip and knee joints, but spinal surgery is typically considered risky.