3 Spondyloarthropathies

• Ankylosing Spondylitis (AS): the prototype disease for our purposes in MJBS. Ankylosis means ‘bony fusion’ and Spondylitis ‘spine inflammation’ referringto the fact that without treatment, these patients can progress to spinal fusion.  (Rheumatologists further subdivide this group into those with and without radiographic findings as well as axial versus peripheral subtypes. These details are beyond the scope of this course but you may come across these terms in your Internal medicine or other clinical rotations.)

Clinical features of AS include the insidious onset of low back pain, usually before 40 years of age, associated with prominent morning stiffness, and improving with exercise and non- steroidal anti-inflammatory agents. Arthritis occurs in peripheral joints in approximately 1/3 of patients. Large joints lower extremity joints such as the sacroiliac (SI) joints, hips, knees and ankles are most often affected though shoulders and elbows and TMJ (jaw) joint can also be involved. Enthesitis may present as recurrent tendonitis or bursitis such as Achilles tendonitis or plantar fasciitis. Pathologically, enthesitis is characterized by inflammation where ligaments attach to bone and cartilaginous erosions secondary to formation of subchondral granulation tissue. Without appropriate treatment, the ongoing joint inflammation in patients with AS may progress to bony fusion (ankylosis) of affected joint structures due to inappropriate ‘healing’ responses. This can result in characteristic changes in the spine (see figure) overtime which are irreversible.

• Psoriatic Arthritis (PsA): though considerable overlap exists with the phenotype of AS including frequent presence of inflammatory back pain, and SI joint involvement, patients with psoriatic arthritis may have unique features including possible dactylitis (dactylitis = inflammation of an entire digit) and more prominent involvement of small joints, including the distal interphalangeal joints (DIPs) in fingers and toes. The rate of Psoriatic arthritis in patients with psoriasis has been difficult to quantify and ranges from 4-30% in certain cohorts. A high index of suspicion for possible joint involvement is warranted for any patients with psoriatic skin disease. Not all patients categorized as having psoriatic arthritis have active skin disease! Skin involvement can flare/occur independently from joint complaints in some patients.  The presence of nail pits on exam is suggestive of risk for joint disease and is thought to indicate the presence of low grade inflammation at entheses in the fingers close to the developing nail bed.

• Reactive arthritis: The classic triad of urethritis (painful inflammation of the urteter), arthritis (often mono- or oligo-articular) and acute painful uveitis (inflammation of the anterior portion of the eye) 2-3 weeks following an infectious illness is known as reactive arthritis. Affected joints tend to be large joints and entheses can also be affected. While this is often a self-limited (resolving) illness, symptoms can last up to 6 weeks to several months in adult patients. Common implicated triggering infections include GI and GU pathogens such as Salmonella, Shigella and Campylobacter or Chlamydia/Gonorrhea. Patients tend to be HLA-B27 positive and may be at risk for repeat episodes of inflammatory arthritis with subsequent infections and/or progression to a more chronic/persistent disease such as AS. In most cases the inciting infection is often resolved (ie the process is post-infectious, immune mediated) but a more acute onset (days) should raise suspicion for a true infectious process. Neisseria gonorrhoeae in particular can spread from the GU track by hematogenous spread and lead to a disseminated infection characterized by septic arthritis and/or tenosynovitis (infectious inflammation of tendon sheaths)

• Inflammatory Bowel Disease (IBD)-related arthritis (aka enteropathic arthrisits):  This type of arthritis occurs in 10-20% of patients with Ulcerative colitis, or Crohn’s disease, but can also follow bacterial dysentery (aka reactive arthritis). Two main forms include:
  1. Peripheral arthritis, especially knees and ankles but also hips, usually associated with active bowel disease; may be associated with erythema nodosum, oral ulcers or uveitis (inflammation of the tissues in the eye from the anterior iris to the more posterior retina).
  2. Ankylosing spondylitis independent of bowel disease activity: in these patients, joint inflammation may precede overt bowel disease. (See section on extra-intestinal manifestations of AS above.)

All of these seronegative spondyloarthropathy patients may have extra-articular disease manifestations such as inflammatory eye disease (acute, painful uveitis), and or inflammatory bowel disease. Approximately 85-90% of AS patients are HLA-B27 positive, however, given the prevalence of this variant in healthy populations (5-12%) this test is not 100% sensitive or specific and should not be used to confirm or refute a diagnosis.  (Top Tip: although enriched in patients with AS and related disorders, only 5-6% of HLA-B27 positive people will develop AS or a related inflammatory condition; patients who are HLA-B27 negative may also develop AS).