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KembaraXtra-Medicine- Ankylosing Spondylitis
Basic Information and Definition
Ankylosing spondylitis (AS) is a chronic inflammatory arthritis that primarily affects the sacroiliac joints and axial skeleton. It is characterized by ankylosis, which is abnormal joint stiffening, and enthesitis, inflammation at tendon and ligament insertion sites. Ankylosing spondylitis belongs to the family of seronegative spondyloarthropathies, which also includes reactive arthritis, psoriatic spondylitis, and enteropathic arthritis.
Synonyms
Ankylosing spondylitis is also known as Marie-Strümpell disease and Bechterew disease.
ICD-10-CM Codes
Ankylosing spondylitis is coded according to the region of spinal involvement, including unspecified spinal sites, juvenile ankylosing spondylitis, and specific cervical, thoracic, lumbar, lumbosacral, sacral, and occipito-atlanto-axial regions.
Epidemiology and Demographics
The prevalence of ankylosing spondylitis ranges from 0.1% to 1% of the general population and varies by ethnicity and the prevalence of the HLA-B27 allele. In populations with HLA-B27 positivity, prevalence is significantly higher, especially among individuals with a family history of spondyloarthropathy. The disease predominantly affects males, with approximately 70% of cases occurring in men. Symptoms typically begin between ages 15 and 35, and most patients develop symptoms before age 45.
Physical Findings and Clinical Presentation
Patients commonly present with chronic inflammatory back pain of insidious onset lasting longer than three months. Morning stiffness lasting at least 30 minutes is typical and improves with physical activity but worsens with rest. Bilateral sacroiliac joint tenderness is common, along with limited lumbar spine mobility. Enthesitis frequently affects the Achilles tendon and plantar fascia. Reduced chest expansion may occur due to costovertebral joint involvement. Peripheral arthritis, usually asymmetric and affecting the lower extremities, may be present. In advanced disease, patients may develop a characteristic posture with loss of lumbar lordosis, fixed hip flexion, knee flexion, and compensatory hyperextension of the neck. Extra-articular manifestations include acute anterior uveitis or iritis, seen in up to 40% of patients, as well as cardiovascular involvement such as aortic insufficiency, pulmonary fibrosis, and increased risk of osteoporosis.
Inflammatory Back Pain Characteristics
Inflammatory back pain in ankylosing spondylitis typically begins before age 45, persists for more than three months, and is localized to the lower back with possible alternating buttock pain. Symptoms often awaken patients during the second half of the night and improve with exercise or nonsteroidal anti-inflammatory drugs, but not with rest.
Etiology and Pathogenesis
The exact cause of ankylosing spondylitis remains incompletely understood. Genetic susceptibility plays a major role, with HLA-B27 being the strongest known predisposing factor. Immune dysregulation, environmental triggers, infections such as Klebsiella pneumoniae, and hormonal influences may contribute to disease development. Tumor necrosis factor (TNF) and other inflammatory cytokines are central mediators of the inflammatory process.
Diagnosis
Diagnosis is based on clinical features, laboratory findings, and imaging. Demonstration of inflammatory sacroiliitis on imaging is diagnostic in most patients, although some meet criteria for nonradiographic axial spondyloarthritis. Elevated erythrocyte sedimentation rate and C-reactive protein may be present, along with mild anemia. HLA-B27 testing supports the diagnosis in appropriate clinical contexts but is not diagnostic on its own, as it is present in a proportion of the healthy population.
Differential Diagnosis
The differential diagnosis includes diffuse idiopathic skeletal hyperostosis, mechanical or noninflammatory back pain, and other inflammatory spondyloarthropathies such as psoriatic arthritis, reactive arthritis, and enteropathic arthritis.
Imaging Studies
Pelvic radiographs classically demonstrate bilateral sacroiliitis and are part of the modified New York criteria. As disease progresses, vertebral bodies lose their normal concavity and become squared, with calcification of spinal ligaments leading to the characteristic bamboo spine appearance. Advanced disease may show diskovertebral erosions known as Andersson lesions. MRI is particularly useful in early disease and can detect active inflammation, bone marrow edema, erosions, and sacroiliitis before changes are visible on plain radiographs.
Nonpharmacologic Treatment
Regular exercise is a cornerstone of management, with emphasis on maintaining spinal mobility, posture, and aerobic fitness. Patients should be instructed in spinal extension and postural exercises to prevent flexion deformities. Sleeping supine on a firm mattress without pillows under the head or knees is recommended. Breathing exercises help preserve chest expansion.
Pharmacologic Therapy
Continuous full-dose NSAIDs are first-line therapy and are effective in controlling pain and stiffness; indomethacin may be particularly effective in some patients. Sulfasalazine may benefit patients with significant peripheral arthritis. Biologic therapies targeting TNF, such as etanercept, infliximab, and adalimumab, are highly effective for patients with inadequate response to NSAIDs and improve symptoms, spinal mobility, and quality of life. Etanercept is generally avoided in patients with recurrent uveitis. Interleukin-17 inhibitors, including secukinumab and ixekizumab, are approved alternatives for active disease.
Disposition and Prognosis
Most patients with ankylosing spondylitis have a normal life expectancy; however, many experience progressive loss of spinal mobility and functional impairment. Early diagnosis and appropriate therapy significantly improve long-term outcomes.
Referral
All patients with suspected or confirmed ankylosing spondylitis should be referred to a rheumatologist for comprehensive evaluation and long-term management.
Pearls and Considerations
A positive family history increases the diagnostic value of HLA-B27 testing. Selected patients with severe spinal deformities may benefit from corrective osteotomy. Emerging evidence suggests an increased risk of cardiovascular and vascular mortality, particularly in men with longstanding disease.
Basic Information and Definition
Ankylosing spondylitis (AS) is a chronic inflammatory arthritis that primarily affects the sacroiliac joints and axial skeleton. It is characterized by ankylosis, which is abnormal joint stiffening, and enthesitis, inflammation at tendon and ligament insertion sites. Ankylosing spondylitis belongs to the family of seronegative spondyloarthropathies, which also includes reactive arthritis, psoriatic spondylitis, and enteropathic arthritis.
Synonyms
Ankylosing spondylitis is also known as Marie-Strümpell disease and Bechterew disease.
ICD-10-CM Codes
Ankylosing spondylitis is coded according to the region of spinal involvement, including unspecified spinal sites, juvenile ankylosing spondylitis, and specific cervical, thoracic, lumbar, lumbosacral, sacral, and occipito-atlanto-axial regions.
Epidemiology and Demographics
The prevalence of ankylosing spondylitis ranges from 0.1% to 1% of the general population and varies by ethnicity and the prevalence of the HLA-B27 allele. In populations with HLA-B27 positivity, prevalence is significantly higher, especially among individuals with a family history of spondyloarthropathy. The disease predominantly affects males, with approximately 70% of cases occurring in men. Symptoms typically begin between ages 15 and 35, and most patients develop symptoms before age 45.
Physical Findings and Clinical Presentation
Patients commonly present with chronic inflammatory back pain of insidious onset lasting longer than three months. Morning stiffness lasting at least 30 minutes is typical and improves with physical activity but worsens with rest. Bilateral sacroiliac joint tenderness is common, along with limited lumbar spine mobility. Enthesitis frequently affects the Achilles tendon and plantar fascia. Reduced chest expansion may occur due to costovertebral joint involvement. Peripheral arthritis, usually asymmetric and affecting the lower extremities, may be present. In advanced disease, patients may develop a characteristic posture with loss of lumbar lordosis, fixed hip flexion, knee flexion, and compensatory hyperextension of the neck. Extra-articular manifestations include acute anterior uveitis or iritis, seen in up to 40% of patients, as well as cardiovascular involvement such as aortic insufficiency, pulmonary fibrosis, and increased risk of osteoporosis.
Inflammatory Back Pain Characteristics
Inflammatory back pain in ankylosing spondylitis typically begins before age 45, persists for more than three months, and is localized to the lower back with possible alternating buttock pain. Symptoms often awaken patients during the second half of the night and improve with exercise or nonsteroidal anti-inflammatory drugs, but not with rest.
Etiology and Pathogenesis
The exact cause of ankylosing spondylitis remains incompletely understood. Genetic susceptibility plays a major role, with HLA-B27 being the strongest known predisposing factor. Immune dysregulation, environmental triggers, infections such as Klebsiella pneumoniae, and hormonal influences may contribute to disease development. Tumor necrosis factor (TNF) and other inflammatory cytokines are central mediators of the inflammatory process.
Diagnosis
Diagnosis is based on clinical features, laboratory findings, and imaging. Demonstration of inflammatory sacroiliitis on imaging is diagnostic in most patients, although some meet criteria for nonradiographic axial spondyloarthritis. Elevated erythrocyte sedimentation rate and C-reactive protein may be present, along with mild anemia. HLA-B27 testing supports the diagnosis in appropriate clinical contexts but is not diagnostic on its own, as it is present in a proportion of the healthy population.
Differential Diagnosis
The differential diagnosis includes diffuse idiopathic skeletal hyperostosis, mechanical or noninflammatory back pain, and other inflammatory spondyloarthropathies such as psoriatic arthritis, reactive arthritis, and enteropathic arthritis.
Imaging Studies
Pelvic radiographs classically demonstrate bilateral sacroiliitis and are part of the modified New York criteria. As disease progresses, vertebral bodies lose their normal concavity and become squared, with calcification of spinal ligaments leading to the characteristic bamboo spine appearance. Advanced disease may show diskovertebral erosions known as Andersson lesions. MRI is particularly useful in early disease and can detect active inflammation, bone marrow edema, erosions, and sacroiliitis before changes are visible on plain radiographs.
Nonpharmacologic Treatment
Regular exercise is a cornerstone of management, with emphasis on maintaining spinal mobility, posture, and aerobic fitness. Patients should be instructed in spinal extension and postural exercises to prevent flexion deformities. Sleeping supine on a firm mattress without pillows under the head or knees is recommended. Breathing exercises help preserve chest expansion.
Pharmacologic Therapy
Continuous full-dose NSAIDs are first-line therapy and are effective in controlling pain and stiffness; indomethacin may be particularly effective in some patients. Sulfasalazine may benefit patients with significant peripheral arthritis. Biologic therapies targeting TNF, such as etanercept, infliximab, and adalimumab, are highly effective for patients with inadequate response to NSAIDs and improve symptoms, spinal mobility, and quality of life. Etanercept is generally avoided in patients with recurrent uveitis. Interleukin-17 inhibitors, including secukinumab and ixekizumab, are approved alternatives for active disease.
Disposition and Prognosis
Most patients with ankylosing spondylitis have a normal life expectancy; however, many experience progressive loss of spinal mobility and functional impairment. Early diagnosis and appropriate therapy significantly improve long-term outcomes.
Referral
All patients with suspected or confirmed ankylosing spondylitis should be referred to a rheumatologist for comprehensive evaluation and long-term management.
Pearls and Considerations
A positive family history increases the diagnostic value of HLA-B27 testing. Selected patients with severe spinal deformities may benefit from corrective osteotomy. Emerging evidence suggests an increased risk of cardiovascular and vascular mortality, particularly in men with longstanding disease.
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