Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease that primarily affects the axial skeleton, especially the sacroiliac joints and spine. It belongs to a group of conditions known as spondyloarthritides and is characterized by progressive inflammation that can lead to structural damage, spinal stiffness, and reduced mobility.
What is it
Ankylosing spondylitis is an immune-mediated inflammatory disorder in which chronic inflammation occurs at the sites where ligaments and tendons attach to bone (entheses), particularly in the spine and sacroiliac joints. Over time, this inflammation can lead to new bone formation, resulting in fusion (ankylosis) of spinal segments and loss of flexibility.
What causes it
The exact cause of AS is not fully understood, but it is strongly associated with genetic factors, especially the presence of the HLA-B27 gene, which is found in most patients with AS. Environmental triggers, such as infections, may activate the immune system in genetically predisposed individuals. The disease involves abnormal immune responses that promote chronic inflammation and pathological bone formation.
What are the symptoms
Symptoms usually begin in late adolescence or early adulthood. The most common symptom is chronic inflammatory back pain, characterized by gradual onset, improvement with exercise, worsening with rest, and night pain. Morning stiffness lasting longer than 30 minutes is typical. Other symptoms include reduced spinal mobility, buttock pain due to sacroiliitis, fatigue, and chest wall stiffness leading to reduced lung expansion. Extra-articular manifestations may include uveitis, enthesitis, peripheral arthritis, inflammatory bowel disease, and, less commonly, cardiac involvement.
How the diagnosis is made
Diagnosis is based on a combination of clinical features, imaging, and laboratory findings. Imaging of the sacroiliac joints is central to diagnosis. X-rays may show sacroiliitis in established disease, while MRI can detect early inflammatory changes before structural damage appears. Blood tests may show elevated inflammatory markers (ESR, CRP), and testing for HLA-B27 supports the diagnosis but is not diagnostic on its own. Classification criteria such as the ASAS criteria are commonly used.
Importance of diagnostic tests
Diagnostic tests are crucial for confirming AS, detecting early disease, distinguishing it from mechanical back pain, and assessing disease activity and progression. MRI is particularly important for identifying early inflammation, allowing diagnosis before irreversible structural changes occur.
Importance of early diagnosis
Early diagnosis is essential because structural damage and spinal fusion can be irreversible. Identifying AS early allows prompt initiation of therapy, which can reduce inflammation, improve symptoms, maintain spinal mobility, prevent deformity, and enhance quality of life. Delayed diagnosis is associated with worse functional outcomes.
Management options
Management aims to control inflammation, relieve pain, and preserve function. Non-steroidal anti-inflammatory drugs (NSAIDs) are first-line treatment. Biologic therapies, particularly tumor necrosis factor (TNF) inhibitors and interleukin-17 inhibitors, are used in patients with active disease not controlled by NSAIDs. Physiotherapy and regular exercise are essential components of care. Posture training, smoking cessation, and patient education are important supportive measures. Surgery may be considered in severe deformity or advanced joint damage.
Prognosis
Ankylosing spondylitis is a chronic, lifelong condition with variable progression. With early diagnosis and modern therapies, many patients achieve good symptom control and maintain functional independence. Without adequate treatment, AS may lead to significant spinal rigidity, disability, and reduced quality of life.
