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Ankylosing spondylitis is a chronic inflammatory disease of spine and pelvis that leads to fusion of the affected joints.
Risk factors:
- HLA-B27 (Human leukocyte antigen B27) association: It is strongly associated with HLA-B27.
- Male gender
- Positive family history
Other conditions associated with HLA-B27:
- Ankylosing spondylitis
- Reiter Syndrome/ Reactive arthritis
- Psoriatic arthritis
- Inflammatory Bowel disease
- Uveitis
Clinical features:
- Usually young male.
- Lower back pain.
- Intermittent hip pain.
- Neck stiffness.
- Enthesopathy: definitive pain at insertion of tendons/ ligaments.
- The pain is increased by inactivity, at the morning and decreases by activity.
Extra-articular manifestations:
- Uveitis.
- Upper lobe fibrosis of lung.
- Aortic regurgitation, 3o Heart block
- Cauda equina syndrome/ conus medullaris
- Psoriasis
Examination:
- Tenderness at
- Sacroiliac joint (Sacroiliitis), earliest manifestation.Sternoclavicular joint.Spinous process of vertebra.
- Tibial tuberosity and heel.
- Buttock muscle atrophy.
- Decreased lateral bending.
- Decreased height due to substantial thoracic kyphosis and loss of lumbar lordosis.
- Decreased chest expansion: <5cm.
- Schober test: decreased spine flexion.
- Modified Schober test.
- Spondyloarthropathy:
- Sausage digits
- psoriasis
- inflammatory backache
- NSAIDs responsive enthesopathy
- Arthritis
- Crohn’s disease/ Inflammatory bowel disease
- HLA-B27 association
How to perform Modified Schober test?
- Locate Posterior superior iliac spine (PSIS).
- Point dots 5cm below and 10 cm above the line joining two PSIS (total length approx. 15cm).
- Ask patient to bend forward and touch the toe.
- Increase in distance between two dots by:
- >5 cm: normal; <4 cm: Restriction in flexibility of spine.
Investigations and work up:
- X-ray lumbosacral spine:
- Sarcoilitis
- loss of lumbar lordosis
- squaring of lumbar vertebra
- Development of vertical syndesmophytes.
- Bamboo spine
- Dragger spine.
- HLA-B27: positive.
- MRI: bone marrow edema.
- Blood tests:
- ESR (Erythrocyte sedimentation rate), CRP (C reactive protein): increased.
- Serum alkaline phosphatase: Increased.
- IgA, C3 levels: Increased.
- Rheumatoid factor: Negative.
- ANA (Anti-nuclear antibody): Negative.
Diagnosis:
Bone marrow edema / Sarcoilitis + 1 spondyloarthropathy feature.
OR, HLA-B27 Positive + 2 spondyloarthropathy feature.
Treatment:
- Exercise: to improve posture and breathing.
- NSAIDs: for pain.
- TNF inhibitors, Sulfasalazine: for refractory cases.
- Methotrexate, Gold salts and steroids have no role.
References:
- Apley & Solomon’s System of Orthopaedics and Trauma, 10th edition.
- Harrison’s Principles of Internal Medicine, 21st edition.
- Robbins Basic Pathology: 10th Edition
