DISORDER · TOPIC
MECHANISM · TRIGGER
FEATURES
CLUE · TREATMENT
HLA-B27 (MHC class I) + IL-23/IL-17 axis; inflammation at entheses
Sacroiliitis, spondylitis, asymmetric oligoarthritis, enthesitis (Achilles, plantar fascia), dactylitis, anterior uveitis
RF and anti-CCP negative
Spinal enthesitis and sacroiliitis
Onset < 40, > 3 months, morning stiffness, improves with exercise, night pain
Mechanical pain improves with rest
Chronic enthesitis → new bone (syndesmophytes) → vertebral fusion
Young men; bilateral sacroiliitis, "bamboo spine," ↓ lumbar flexion and chest expansion, kyphosis
NSAIDs, TNF or IL-17 inhibitors
Ankylosing spondylitis — extra-spinal
Inflammation of eye, aortic root, lung apex
Anterior uveitis, aortic regurgitation (aortitis), heart block, apical lung fibrosis, vertebral fractures after minor trauma
Fused spine fractures easily
Weeks after GI (Shigella, Salmonella, Yersinia, Campylobacter) or GU (Chlamydia) infection; sterile joints
Asymmetric knee/ankle arthritis + conjunctivitis + urethritis; keratoderma blennorrhagicum, circinate balanitis
"Can't see, can't pee, can't climb a tree"
Psoriasis-associated; may precede skin disease
DIP involvement, dactylitis ("sausage digits"), nail pitting and onycholysis; asymmetric; arthritis mutilans
"Pencil-in-cup" erosion on X-ray
Crohn disease, ulcerative colitis
Peripheral arthritis follows bowel activity; axial disease runs its own course
Treat the IBD; TNF inhibitors cover both
Diffuse idiopathic skeletal hyperostosis
Noninflammatory ligament ossification; older, obese, diabetic
"Flowing" ossification of anterior longitudinal ligament (≥ 4 vertebrae, right side of thoracic spine); SI joints spared
Mimic of AS
Erosion then new bone
Sacroiliitis (MRI earliest), syndesmophytes, squaring of vertebrae, "shiny corners"
Bamboo spine = late AS
Suppress inflammation
NSAIDs first; TNF inhibitors, IL-17 (secukinumab), IL-12/23 (ustekinumab); methotrexate for peripheral (psoriatic) arthritis
Physical therapy for spine mobility