Spondyloarthritides

Family of inflammatory arthritides characterized by axial skeletal involvement (sacroiliac joints, spine), enthesitis (inflammation at tendon/ligament insertions), and a strong association with HLA‑B27. They are seronegative (negative rheumatoid factor) and include ankylosing spondylitis, psoriatic arthritis, reactive arthritis, IBD-associated arthritis, and others.

• These disorders often strike young adults, causing chronic pain and disability (spinal fusion, joint destruction) if untreated. They commonly appear on exams linking back pain with eye, skin, or GI symptoms (e.g., uveitis, psoriasis, colitis). Recognizing inflammatory back pain (improves with exercise, not rest) and the classic extra-articular features can differentiate spondyloarthritides from more common back pain etiologies.

• Young patients (typically age <40) with chronic low back pain and morning stiffness >30 minutes that improves with activity (inflammatory back pain). Pain often insidious in onset and may awaken in the second half of the night; may have alternating buttock pain (from sacroiliitis).
• Asymmetric peripheral arthritis can occur (especially lower limbs). Characteristic dactylitis ("sausage digits" – diffuse swelling of a finger/toe) and enthesitis (tender insertion of Achilles tendon or plantar fascia) are common clues, especially in psoriatic or reactive arthritis.
• Extra-articular features: acute anterior uveitis (unilateral eye pain, redness, photophobia) in ~25% of patients with ankylosing spondylitis; psoriatic skin lesions and nail pitting in psoriatic arthritis; inflammatory bowel disease (Crohn or ulcerative colitis) in enteropathic arthritis; history of recent GI or GU infection in reactive arthritis. Often HLA‑B27 positive (e.g., >90% in ankylosing spondylitis; ~50% in others), and ESR/CRP elevated during active disease.

1. Recognize inflammatory back pain: age <40, insidious onset, >3 months duration, morning stiffness improved by exercise (vs mechanical back pain which worsens with activity and improves with rest). These features → evaluate for spondyloarthritis.
2. Imaging is key: start with X-ray of the sacroiliac joints – look for sacroiliitis (subchondral sclerosis, erosions, eventual fusion). If X-ray is normal but clinical suspicion is high (early disease), get an MRI of SI joints to catch active inflammation or erosion.
3. Lab tests: HLA‑B27 testing is supportive (not diagnostic) – strongly positive in AS, variably in others. Inflammatory markers (ESR, CRP) are often elevated. Rheumatoid factor and anti-CCP are characteristically negative (hence "seronegative").
4. Distinguish from other arthritides: spondyloarthritides usually have asymmetric arthritis (often lower extremities) and spinal involvement. In contrast, rheumatoid arthritis is symmetric, primarily hands/feet, and usually spares the spine (except cervical). Also check for DIP joint involvement or dactylitis (seen in psoriatic, not RA).
5. If peripheral joints are significantly involved, perform arthrocentesis for any acutely swollen joint to exclude septic arthritis or crystalline arthritis – spondyloarthritis can coexist with these, so don't miss an infection.

1. NSAIDs (e.g., naproxen, indomethacin) are first-line for pain and stiffness (often dramatic benefit in ankylosing spondylitis). Encourage exercise and physical therapy to maintain posture and mobility, especially in axial disease.
2. Sulfasalazine or methotrexate can help peripheral arthritis (e.g., in psoriatic or IBD-associated arthritis), but these conventional DMARDs do not significantly help axial symptoms.
3. For advanced or refractory disease, especially axial involvement, use biologic agents: TNF-α inhibitors (eg, infliximab, etanercept) or IL-17 inhibitors (eg, secukinumab) which can reduce inflammation and slow progression. (In psoriatic arthritis, IL-12/23 inhibitors or PDE4 inhibitors like apremilast are additional options.)
4. Treat associated conditions: e.g., topical or systemic therapy for psoriasis, antibiotics for underlying infection in reactive arthritis (treat chlamydia if present), and optimal control of IBD. Local corticosteroid injections can help enthesitis or a persistently inflamed peripheral joint; however, systemic glucocorticoids are generally not used long-term (they're not very effective for axial disease).
5. Multidisciplinary care: coordinate between rheumatology, ophthalmology (for uveitis management with local steroids), dermatology (psoriasis management), and gastroenterology (IBD therapy) as needed.

• Remember PAIR: Psoriatic arthritis, Ankylosing spondylitis, IBD-related arthritis, Reactive arthritis – the major spondyloarthritides.
• Sausage digit (dactylitis) on exam → think psoriatic or reactive arthritis (seronegative) rather than RA.
• Inflammatory back pain (morning stiffness, better with exercise) in a young adult is a red flag for spondyloarthritis.
• Classic teaching: "Can't see, can't pee, can't climb a tree" – refers to the triad of conjunctivitis, urethritis, and arthritis in reactive arthritis.

• Back pain with red flag features (unexplained weight loss, fever, nighttime pain unrelieved by movement, neurologic deficits) → consider infection or malignancy in the spine rather than assuming spondyloarthritis.
• Known ankylosing spondylitis with sudden severe back pain or neurologic signs after minor trauma → suspect a spinal fracture in a brittle fused spine (requires urgent imaging). Also, watch for signs of cauda equina syndrome (incontinence, saddle anesthesia) in longstanding AS, which is rare but serious.
• Do not overlook a septic joint: if a spondyloarthritis patient has an acutely hot, swollen joint with fever, perform arthrocentesis – they can still get septic arthritis, which is an emergency.

1. Chronic back pain age <40 with inflammatory features (morning stiffness, better with exercise) → suspect spondyloarthritis.
2. Obtain pelvic X-ray (SI joints): if sacroiliitis is present, that supports diagnosis (ankylosing spondylitis if criteria met). If X-ray normal but suspicion high, do MRI of SI joints.
3. Check HLA-B27 status and inflammatory markers (ESR/CRP); negative RF/CCP helps exclude RA if peripheral joints involved.
4. Identify subtype: look for psoriasis (→ psoriatic), IBD history (→ enteropathic), recent infection (→ reactive), or just isolated axial disease (ankylosing spondylitis).
5. Start NSAIDs and exercise for axial symptoms; refer to rheumatology for further management. Treat any underlying trigger (infection or IBD) and involve appropriate specialists. Escalate to biologics if needed for uncontrolled disease.

• 28-year-old man with 6 months of low back pain and stiffness that improves throughout the day, limited chest expansion, and X-ray showing bilateral sacroiliitis → Ankylosing spondylitis.
• 45-year-old patient with psoriasis develops nail pitting and a swollen, painful finger ("sausage digit") involving the DIP joint → Psoriatic arthritis.
• 23-year-old man, 2 weeks after a dysenteric diarrhea, now has knee and ankle arthritis and urethral discharge with conjunctivitis → Reactive arthritis (Reiter syndrome).
• 35-year-old woman with Crohn's disease flares who experiences knee arthritis during flares and back stiffness even in remission → Enteropathic (IBD-associated) arthritis.