Chapter 98. Ankylosing Spondylitis

A 43-year-old man falls and presents with acute back and diffuse abdominal pain. He has had back pain on and off for years. Also, his wife notes that he has become “stooped” forward in the last few years. The radiographs show flowing ligamentous ossification and syndesmophyte formation about the cervical, thoracic, and lumbar spine consistent with ankylosing spondylitis (bamboo spine) (Figure 98-1). The KUB (kidneys, ureters, bladder) view film also shows fusion of the sacroiliac joints consistent with ankylosing spondylitis (Figure 98-2). No fracture, dislocation, or abdominal pathology is identified. The patient's symptoms are treated and nonsteroidal antiinflammatory drugs (NSAIDs) are started. On follow-up a blood test reveals that he is human leukocyte antigen (HLA)-B27-positive.

Ankylosing spondylitis is an inflammatory disease of the axial spine associated with the HLA-B27 genotype. Symptoms of low back and/or hip pain begin in late adolescence or early adulthood. Diagnosis is based on clinical features and radiographic findings.

• Prevalence in general population is approximately 0.2% to 0.5%.
• Five percent of patients in primary care with low back pain have a spondyloarthritis, a spectrum of diseases that includes ankylosing spondylitis.1
• More common in males than in females (approximate ratio: 4:1).
• Ninety percent of patients are HLA-B27-positive.2 However, many people with HLA-B27 do not develop the disease.

• Inflammatory arthritis with a poorly understood pathology.
• Environment and genetic factors result in inflammation.
• Chronic inflammation causes in extensive new bone formation.

• Male gender.
• HLA-B27-positive genotype.

Mean delay of 7 to 8 years until diagnosis. Consider screening patients younger than 45 years of age with chronic low back pain for more than 3 months.3

Clinical Features

• Younger patient (younger than 40 years of age at start of disease).
• Inflammatory (pain and stiffness worsen with immobility and improve with motion; symptoms are worse at night or early morning).
• Good response to NSAIDs—Sensitivity = 77%, specificity = 85%, positive likelihood ratio (LR+) 5.1.1
• Symptoms of inflammatory back pain have fair sensitivity (75%) and specificity (75%). LR+ 3.1. Number needed to screen is 7.1,3

Physical Exam

• Limited range of motion of the spine.
• Tenderness over the spine and sacroiliac joints.
• In the advanced stages, kyphosis may occur with a stooped posture (Figure 98-1).
• Uveitis of the eye is the most common extraarticular manifestation occurring in 20% to 30% of patients. This can present with a red painful eye along with photophobia. The involved eye may have an irregular pupil and a 360-degree perilimbal injection (see Chapter 18, Uveitis and Iritis).

Typical Distribution

• Pain in lower back and/or sacroiliac joints.

Laboratory Testing

• HLA-B27 has good sensitivity (90%) and specificity (90%). LR+ 9.0. Number needed to screen is 3. Test is expensive.1,3
• May also consider HLA-B27 for patients with inflammatory back pain only.1

Imaging

• Radiologic findings confirm the diagnosis; however, these may occur years after the onset of symptoms.
• Plain films—Typical spinal features include erosions, squaring, sclerosis, syndesmophytes, and fractures; may also see sacroiliac joint fusion (Figure 98-3). Flowing ligamentous ossification and syndesmophyte formation about the cervical, thoracic, and lumbar spine form the classic bamboo spine described in ankylosing spondylitis (Figures 98-1 and 98-2).
• MRI—Detects inflammation, such as acute sacroiliitis, which occurs prior to bony change visible by radiographs.

Causes of back pain in patients younger than age 45 years:

• Lumbar strain or muscle spasm—Acute onset often with precipitating event.
• Herniated disc—Acute onset with pain radiating below the knee into lower leg or foot with numbness, weakness, and/or loss of ankle jerk reflex.
• Vertebral fractures—Risk factors are osteoporosis or significant trauma.
• Abdominal pathology such as pancreatitis—Associated with GI symptoms.
• Kidney diseases—Nephrolithiasis (pain radiating into groin); pyelonephritis (fever, nausea, and urinary symptoms).
• Osteoarthritis—Worse after working; less commonly has inflammatory symptoms.
• Other spondyloarthritides (SpA) include psoriatic spondyloarthritis (Figure 98-4), SpA associated with inflammatory bowel disease, reactive SpA, and undifferentiated SpA.

• NSAIDs and physical therapy reduce pain. Continuous NSAIDs reduce radiographic progression.4 SOR B
• Disease-modifying antirheumatic drugs (methotrexate, leflunomide) have not been demonstrated to have patient-oriented outcomes.4 SOR B
• Tissue necrosis factor blockers are recommended for patients who fail NSAIDs and physical therapy. Consider treating or referring for treatment with shorter duration of symptoms, elevated acute phase reactants (i.e., C-reactive protein), or rapid radiographic progression. SOR C
  • Infliximab improves pain scores and quality of life within 2 weeks (61% vs. 19% placebo).4 SOR B Many relapse; high cost, but economic analysis is favorable compared to estimated cost of loss of function.4
  • Adalimumab improves quality-of-life and function scores by 12 weeks. Improvement continues for up to a year and remains stable through 3 years.5 SOR B
  • Etanercept improves pain scores (60% vs. 12%).4 SOR B Relief within 2 weeks. Many relapse; reinitiation works.4 Seventy-six percent of patients treated with Etanercept, compared to 53% of patients treated with sulfasalazine, improved by 20% within 4 months.6 Improvements in pain, function, and mobility were sustained at 5 years.7

Mortality is increased in male patients with ankylosing spondylitis. Leading cause of death was cardiovascular. Risk factors for reduced survival include absence of NSAID use (odds ratio [OR] 4.35), work disability (OR 3.65), increased C-reactive protein (OR 2.68), and diagnostic delay (OR 1.05).8

Follow patients for progression of pain or decreased function using standard ankylosing spondylitis, such as the Ankylosing Spondylitis Disease Activity Score or the Bath Ankylosing Spondylitis Disease Activity Index or Functional Index.

Ankylosing spondylitis is a chronic disease. NSAIDs and physical therapy and exercise are important in controlling pain and slowing progression of disease. If these are ineffective, tissue necrosis factor blockers are effective; however, these are expensive and pain recurs when they are stopped.

Patient Resources

• American College of Rheumatology. Patient education handout: Spondylarthritis (Spondylarthropathy)—http://www.rheumatology.org/practice/clinical/patients/diseases_and_conditions/spondyloarthritis.asp.
• The Spondylitis Association of America—http://www.spondylitis.org.
• PubMed Health. Ankylosing Spondylitis—http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001457/.

Provider Resources

• Assessment of SpondyloArthritis International Society. Ankylosing Spondylitis Disease Activity Score Information and Online Calculator— http://www.Asas-Group.Org/Research.Php?Id=01#Null.
• Medscape. Brent LH. Ankylosing Spondylitis and Undifferentiated Spondyloarthropathy—http://emedicine.medscape.com/article/332945.
• Assessment of SpondyloArthritis International Society (ASAS) and European League Against Rheumatism (EULAR); Zochling J, van der Heijde D, Burgos-Vargas R, et al. ASAS/EULAR recommendations for the management of ankylosing spondylitis. Ann Rheum Dis. 2006;65(4):442-452.—http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1798102/.