4 Ankylosing Spondylitis A pain in the back

Learning Objectives • to identify the typical patient with AS • to differentiate AS from mechanical trauma, lumbago, sciatica or psoriatic arthritis, both clinically and through laboratory testing • to provide examples directing family practitioners when to refer patients to a rheumatologist • to describe different therapies helpful in improving the quality of life for patients living with this highly variable disease

CASE: A 30-year-old male presents to his family doctor with a six-month history of back pain. Currently, the pain is in the midline lower back and radiates into the buttock region bilaterally. He reports it is aggravated by his daily activities and also awakens him frequently at night. On direct questioning, he admits to being very stiff and sore first thing in the morning and somewhat less after doing his exercises and taking a hot shower. The patient’s background history is notable for a similar pain of several months’ duration in his late teens, which he attributed to his summer job of landscaping. He also reports

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that as a teenager he had plantar fasciitis for six months, which eventually settled after the introduction of orthotics. He recalls stopping some of his sports activities in high school due to persistent hip pain that subsequently resolved. EPIDEMIOLOGY AND CLINICAL PRESENTATION Ankylosing spondylitis (AS), a chronic inflammatory disorder of the axial skeleton, strikes an estimated 13 out of 1,000 people, most often adolescent and young adult males. While sacroiliitis is the hallmark of the disorder, hip and shoulder joints and even peripheral joints may also be involved. Ankylosing spondylitis can

ANKYLOSING SPONDYLITIS

be associated with inflammatory bowel disease (Crohn’s and colitis). An asymmetrical form of ankylosing spondylitis and arthritis can also be seen with reactive arthritis (previously known as Reiter’s syndrome) and psoriasis. Some patients have only sacroiliitis and do not have spinal involvement. About 30% do progress to fusion of the spine over the course of about 10 to 15 years. Lower back pain extending to the buttocks and even the thighs is the first presentation in about three quarters of the patients, and the pain is inflammatory in timing. This means that it is prominent in the morning for more than 30 or 40 minutes, and sometimes wakens the patient from sleep. It is alleviated by activity. As the heel pain in the above patient exemplifies, enthesitis (inflammation at sites where tendons attach to bone), can manifest as plantar fasciitis or achilles tendonitis. Extraskeletal manifestations may include anterior uveitis, prostatitis, aortic insufficiency and heart block. DIFFERENTIAL DIAGNOSIS As the pain is inflammatory in timing, affecting young people, especially males, one must think about infectious sacroiliitis or

paraspinal abscess, particularly if there is a history of drug abuse; and also oteoid osteoma which can have a similar pain pattern. Mechanical, discogenic or traumatic causes should be easily ruled out by the timing and nature of the pain as well as the history and physical examination. Special attention must be paid to women presenting with back pain, as their features of AS may be atypical and dismissed as mechanical pain, or related to gynecological pathology or childbirth. ASSOCIATED CONDITIONS It is important to look for associated conditions with sacroiliitis or ankylosing spondylitis. Psoriatic arthritis is seen in about 10% of psoriatics, especially with nail and scalp involvement. Fingers or toes may become purple and swollen. An entire digit may be involved, including tenosynovial sheath and periostium (dactylitis) and/or single or multiple small or medium size joints may become inflamed in an asymmetrical distribution. Unilateral or asymmetrical sacroiliitis or spondylitis may be seen. Reactive arthritis may have similarities to psoriatic arthritis except it starts abruptly and has extraarticular manifestation. It is probably induced by an infective

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ANKYLOSING SPONDYLITIS

AS DIAGNOSIS AT A GLANCE •

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•

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Symptoms: Waking with back pain, either from middle of sleep, or in the morning with more than 30 minutes of morning stiffness Signs: Limited lumbar movement, tender sacroiliac joints to stress, sternomanubrial tenderness, calcaneal tenderness, extraarticular features Investigations: Sacroiliitis on X-ray (sine qua non of the diagnosis). ESR elevation. HLA B27 antigen screening test in equivocal cases Differential diagnosis: Septic sacroiliitis, osteoid osteoma, spondylolisthesis or herniated disc. Associated psoriasis, bowel inflammation or reactive arthritis

agent through sexual contact or bowel infections. Ulcerative colitis or Crohn’s disease may present with a nondestructive large or medium joint inflammation that often becomes bilateral. Symmetrical sacroiliitis and ankylosing spondylitis occur in some of these patients. INVESTIGATION Sacroiliitis on X-ray is the single most important finding for the diagnosis. Caveats occur when findings are equivocal, or epiphyses are not yet fused in young patients. Under these conditions, HLA B27 antigen test may swing the level of suspicion for the diagnosis but should not be done as a screening test for an individual presenting with back pain. In some circumstances, an MRI of the

Fig. 1: Ankylosing spondylitis: sacroiliitis (roentgenogram)

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ANKYLOSING SPONDYLITIS

WHEN TO REFER •

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A confirmed case should see a rheumatologist for initial measurements to follow progress (yearly) Confirmation of diagnosis and rule out associated conditions Refractory pain or loss of function Extra-articular manifestations

sacroiliac joints can provide extra confirmatory detail. Elevated sedimentation rate or C-reactive protein is seen in up to 75%. Slight normocytic, normochromic anemia is possible. These patients have negative ANA and rheumatoid factor. EXPECTED COURSE AND MANAGEMENT Ankylosing spondylitis follows exacerbations and remissions. Some patients eventually accumulate lost movement leading to rigidity of the entire spine. Hips and/or shoulders are involved in 50%, and other peripheral joints in 20% of patients. Early referral to a well-trained physiotherapist or rehabilitation program for education on home exercises will do much to avoid a kyphosis. Periodic reinforcement of these programs is desirable. Nonsteroidal

anti-inflammatory drugs can be very effective and enable good exercise compliance. Advanced rigid cases are susceptible to spinal fractures presenting as refractory pain after minor trauma. Total hip joint replacement and spinal osteotomy are approaches for advanced kyphosis. Salazopyrine or methotrexate and local steroid injections may be helpful in patients with peripheral joint inflammation. Newer agents, such as TNF inhibitors, may have a role in refractory patients. Treatment • Yearly measurement to evaluate posture and range • Educational program on maintenance exercises with regular reinforcement • NSAIDs regularly with appropriate cytoprotection and monitoring • DMARDs in severe cases • Surgery as indicated for hips or kyphosis

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ANKYLOSING SPONDYLITIS

DIAGNOSTIC SUMMARY Inflammatory vs mechanical back pain Feature Age & type of onset Morning stiffness Effect of activity on pain

Inflammatory usually < age 35 > 30 minutes eases with activity

Nocturnal waking

often wakens with pain & must rise for relief

X-ray findings

sacroiliitis, syndesmophytes

Peripheral joint involvement

inflammatory: 50% have shoulder/hip 20% have peripheral joint

QUESTIONS 1. What are the classical features of ankylosing spondylitis? Onset is early — usually in late teens or early adulthood, rarely after 40 — and gradual. The pain is often difficult to localize initially, though it is often severe enough to cause nocturnal awakening. Morning stiffness, lasting 30 minutes or longer, improves with heat and stretching exercises. Axial joints are often affected in a caudad-tocephalad progression. Common peripheral manifestations include hip and shoulder involvement as well as enthesitis. Females may not present ‘classically’.

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Non-inflammatory usually > age 35 < 30 minutes worse after activity & at end of the day aches on getting comfortable in bed, does not waken no sacroiliitis; osteophytes, sclerosis and narrowed facets & discs no association

2. What is the role of HLA B27 in establishing the diagnosis of an inflammatory spondyloarthropathy? Approximately 7% to 8% of all caucasians are HLA positive. Thus, HLA positivity alone does not establish a diagnosis of ankylosing spondylitis. However, when associated with early onset back pain with the clinical and radiographic features of inflammatory back disease, the test has strong diagnostic value. Reactive arthritis, and to a lesser extent psoriatic and enteropathic spondyloarthritis, are also associated with HLA B27 positivity.