Ankylosing spondylitis overview

# Overview
Galen was the first to distinguish the difference between ankylosing spondylitis (AS) and rheumatoid arthritis (RA). Realdo Colombo has first described ankylosing spondylitis. Bernard Connor was first to describe pathological changes occurring in ankylosing spondylitis. Axial spondyloarthritis (axSpA) may be classified according to Assessment of SpondyloArthritis International Society (ASAS) into ankylosing spondylitis (AS) and non-radiographicaxSpA (nr-axSpA). AS has been regarded as the prototype of spondyloarthritis. Ankylosing spondylitis (AS) is a chronic, multisystem inflammatory disorder involving primarily the sacroiliac (SI) joints and the axial skeleton. The outcome in patients with a spondyloarthropathy, including AS, is generally compared with that in patients with a disease such as rheumatoid arthritis. Mostly the joints where the spine joins the pelvis are also affected. Back pain is one of the most prominent symptoms of the ankylosing spondylitis (AS) which is intermittent in nature. Stiffness in the affected joints gets worse as the disease progresses. It is believed that both the combination of genetic and environmental factors play an important role in the pathogenesis of ankylosing spondylitis(AS) and the underlying etiology is believed to be autoimmune or autoinflammatory. Ankylosing spondylitis is an inflammatory disease that in overtime it causes some of the vertebrae in spine to fuse. Because of the fusion the spine less flexible and the patients present with hunched-forward posture. It can be difficult to breathe deeply when the ribs are involved. The most common cause of ankylosing spondylitis is involvement of gene HLA B27. Ankylosing spondylitis must be differentiated from other diseases causing reactive arthritis,rheumatoid arthritis and psoriatic arthritis. The prevalence of axial spondyloarthritis (axSpA) or ankylosing spondylitis in a population depends upon the following 1)Ethnic groups 2) Selection of subjects for evaluation and 3) The criteria for diagnosis.It shows a clear evidence that correlation between the prevalence of ankylosing spondylitis (AS)/axial spondyloarthritis (axSpA) in a given population and the prevalence of human leukocyte antigen HLA-B27 exits. There is no known cause specific cause for ankylosing spondylitis, though genetic factors seems to play very important role in developing the disease. In particular, people who are positive for HLA-B27 are at more risk of developing ankylosing spondylitis.Ankylosing spondylitis is a form of chronic joint inflammation that mostly affects the spine. Gradually it can cause the bones of the spine to fuse together, a process which is called ankylosis. Ankylosing spondylitis symptoms can range from back pain and stiffness and in long term it can lead to disability. Ankylosing spondylitis is usually remarkable for involvement of axial joints, peripheral joints, and entheses. Physical examination of AS includes a typical diagnostic process that includes exams and tests. The physical examination of AS includes cervical spine, thoracic spine, lateral spinal flexion, Schober test, sacroiliac joint tenderness test and hip joint tests. An x-ray may be helpful in the diagnosis of ankylosing spondylitis (AS). Findings on an x-ray suggestive of ankylosing spondylitis (AS) include erosion and ankylosis of the sacroiliac joints. Findings on CT scan suggestive of ankylosing spondylitis include erosion, osteoporosis / sclerosis, and new bone formation. However,CT has poor ability to detect soft-tissue changes and best in detecting osteoporosis or osteosclerosis. Findings on MRI suggestive of ankylosing spondylitisinclude sacroiliitis, disease activity,cartilage condition and enthesitis. MRI allows assessment of all of the structures that are involved in musculoskeletal diseases. Pharmacologic medical therapies for ankylosing spondylitis(AS) include Nonsteroidal anti-inflammatory drugs(NSAIDs), tumor necrosis factor (TNF) blocker, and interleukin 17 (IL-17) inhibitors.

# Historical Perspective
Galen was the first to distinguish the difference between ankylosing spondylitis (AS) and rheumatoid arthritis (RA). Realdo Colombo has first described ankylosing spondylitis. Bernard Connor was first to describe pathological changes occurring in ankylosing spondylitis.

# Classification
Axial spondyloarthritis (axSpA) may be classified according to Assessment of SpondyloArthritis International Society (ASAS) into ankylosing spondylitis (AS) and non-radiographicaxSpA (nr-axSpA). Formerly ankylosing spondylitis (AS) was termed as spondyloarthritides or spondyloarthropathies. AS has been regarded as the prototype of spondyloarthritis. Previously ankylosing spondylitis (AS), spondyloarthritis (SpA), reactive arthritis, psoriatic arthritis, arthritis and spondylitis associated with Crohn disease and ulcerative colitis which belong to inflammatory bowel disease (IBD).

# Pathophysiology
Ankylosing spondylitis (AS), a spondyloarthropathy, is a chronic, multisystem inflammatory disorder involving primarily the sacroiliac (SI) joints and the axial skeleton. The outcome in patients with a spondyloarthropathy, including AS, is generally compared with that in patients with a disease such as rheumatoid arthritis. Mostly the joints where the spine joins the pelvis are also affected. Back pain is one of the most prominent symptoms of the ankylosing spondylitis (AS) which is intermittent in nature. Stiffness in the affected joints gets worse as the disease progresses. It is believed that both the combination of genetic and environmental factors play an important role in the pathogenesis of ankylosing spondylitis(AS) and the underlying etiology is believed to be autoimmune or autoinflammatory.

# Causes
Ankylosing spondylitis is an inflammatory disease that in overtime it causes some of the vertebrae in spine to fuse. Because of the fusion the spine less flexible and the patients present with hunched-forward posture. It can be difficult to breathe deeply when the ribs are involved. The most common cause of ankylosing spondylitis is involvement of gene HLA B27.

# Differentiating from Other Diseases
Ankylosing spondylitis must be differentiated from other diseases causing reactive arthritis,rheumatoid arthritis and psoriatic arthritis.

# Epidemiology and Demographics
The prevalence of axial spondyloarthritis (axSpA) or ankylosing spondylitis in a population depends upon the following 1)Ethnic groups 2) Selection of subjects for evaluation and 3) The criteria for diagnosis.It shows a clear evidence that correlation between the prevalence of ankylosing spondylitis (AS)/axial spondyloarthritis (axSpA) in a given population and the prevalence of human leukocyte antigen HLA-B27 exits.

# Risk Factors
There is no known cause specific cause for ankylosing spondylitis, though genetic factors seems to play very important role in developing the disease. In particular, people who are positive for HLA-B27 are at more risk of developing ankylosing spondylitis.Ankylosing spondylitis is a form of chronic joint inflammation that mostly affects the spine. Gradually it can cause the bones of the spine to fuse together, a process which is called ankylosis.

# Natural History, Complications, and Prognosis
The natural history of ankylosing spondylitis(AS) remains poorly documented. Documentation of the early course of ankylosing spondylitis (AS) has been limited by the lack of appropriate criteria to diagnose early. New York criteria plays an important role in the study of ankylosing spondylitis (AS).

# Diagnosis

## History and Symptoms
Ankylosing spondylitis is a form of arthritis which is progressive and painful. In ankylosing spondylitis some or all of the joints and bones of the spine fuse together and causes pain and restriction of the movement of the spine.The spinal involvement is more extensive in ankylosing spondylitis (AS). Ankylosing spondylitis symptoms can range from back pain and stiffness and in long term it can lead to disability.Although cause of ankylosing spondylitis is unknown but mostly it is associated with genetic marker called HLA-B27.

## Physical Examination
Ankylosing spondylitis is usually remarkable for involvement of axial joints, peripheral joints, and entheses. Physical examination of AS includes a typical diagnostic process that includes exams and tests. The physical examination of AS includes cervical spine, thoracic spine, lateral spinal flexion, Schober test, sacroiliac joint tenderness test and hip joint tests.

## Laboratory Findings
There are no specific diagnostic laboratory findings associated with ankylosing spondylitis (AS). There are certain blood tests that can check for markers of inflammation.Most of the time patients with AS their blood is tested for the HLA-B27 gene, but again most people who are positive for that gene don't have ankylosing spondylitis. Other laboratory findings consistent with ankylosing spondylitis (AS) include ESR and CRP levels.

## X-ray
An x-ray may be helpful in the diagnosis of ankylosing spondylitis (AS). Findings on an x-ray suggestive of ankylosing spondylitis (AS) include erosion and ankylosis of the sacroiliac joints.

## CT scan
CT allows direct visualization of the abnormalities in peripheral and axial joints. CT has resulted in a major improvement in the evaluation and management of patients with AS. Findings on CT scan suggestive of ankylosing spondylitis include erosion, osteoporosis / sclerosis, and new bone formation. However,CT has poor ability to detect soft-tissue changes and best in detecting osteoporosis or osteosclerosis.

## MRI
MRI may be helpful in the diagnosis of ankylosing spondylitis. Findings on MRI suggestive of ankylosing spondylitisinclude sacroiliitis, disease activity,cartilage condition and enthesitis. MRI allows assessment of all of the structures that are involved in musculoskeletal diseases. MRI is more sensitive in inflammatory and degenerative rheumatological disorders. However, not all patients with nr-axSpA have abnormal MRI findings.

# Treatment

## Medical Therapy
Pharmacologic medical therapies for ankylosing spondylitis(AS) include Nonsteroidal anti-inflammatory drugs(NSAIDs), tumor necrosis factor (TNF) blocker, and interleukin 17 (IL-17) inhibitors. Ankylosing spondylitis (AS) is a chronic inflammatory disease which is manifested by back pain and gradually to spinal stiffness.While treating the AS patients the primary goal is to maximize long-term health-related quality of life.

## Surgery
Surgery is not the first-line treatment option for patients with ankylosing spondylitis. Surgical options, such as knee and hip replacements, can be an option for patients with ankylosing spondylitis. Surgical correction is also possible for those with severe flexion deformities, such as a severe downward curvature of the spine.

# Prevention

## Primary Prevention
There are no established measures for the primary prevention of ankylosing spondylitis.

## Secondary Prevention
There are no established measures for the secondary prevention of ankylosing spondylitis.