Ankylosing Spondylitis (Axial Spondyloarthritis)

**Ankylosing spondylitis (AS)** is a chronic inflammatory autoimmune disease where the immune system attacks the joints and ligamentous attachments of the spine and SI joints. This causes inflammation, pain, and over time, new bone formation that can fuse vertebrae together — creating the characteristic "bamboo spine" appearance. **The Spondyloarthropathy Family:** AS is part of a broader family of related autoimmune conditions: - **Ankylosing spondylitis** (now called radiographic axial spondyloarthritis) - **Non-radiographic axial spondyloarthritis** (early stage; no X-ray changes yet) - **[Psoriatic arthritis](/condition/psoriatic-arthritis)** — associated with skin psoriasis - **Reactive arthritis** — triggered by infections - **Enteropathic arthritis** — associated with inflammatory bowel disease - **Juvenile spondyloarthritis** — affects children **Key Pathological Features:** **1. Inflammation (Initial Phase):** - Sacroiliitis — inflammation of the SI joints (almost always present) - Spondylitis — inflammation of the vertebrae - Enthesitis — inflammation where ligaments/tendons attach to bone (Achilles, plantar fascia, costovertebral) - Peripheral arthritis in 30-50% (especially hips, shoulders, knees) **2. New Bone Formation (Late Phase):** - Syndesmophytes — vertical bone bridges between vertebrae - Eventual fusion (ankylosis) of vertebrae - "Bamboo spine" appearance on X-ray - Loss of spinal mobility in all directions **3. Extra-Articular Manifestations:** - **Uveitis (eye inflammation)** in 25-40% — often the first symptom - **Inflammatory bowel disease** in 5-10% - **Psoriasis** in 10% - **Aortic root inflammation** — increased cardiovascular risk - **Pulmonary fibrosis** in late stages - **Cauda equina syndrome** rarely **HLA-B27 — The Genetic Marker:** The HLA-B27 gene is present in 90-95% of AS patients (vs 8% of general population). However, only 1-2% of HLA-B27 positive individuals develop AS — the gene is NECESSARY but not SUFFICIENT. Other genetic and environmental factors play a role.

## Root Causes **Ankylosing spondylitis is an autoimmune condition with strong genetic predisposition:** **1. Genetic Factors (Major):** - **HLA-B27 gene**: Present in 90-95% of AS patients - However, only 1-2% of HLA-B27 carriers develop AS - Other genes contribute (ERAP1, IL-23R, IL-1) - **Family history**: First-degree relatives have 12-30% risk if HLA-B27 positive **2. Immune System Dysfunction:** - Aberrant immune response targeting the joints - IL-23/IL-17 pathway central to disease - TNF-alpha drives inflammation - These targets explain why biologic medications work **3. Environmental Triggers (Possible):** - **Gut microbiome dysbiosis** — emerging evidence - **Bacterial infections** may trigger in susceptible individuals - **Mechanical stress** at entheses (where ligaments attach to bone) - **Smoking** — significantly worsens disease progression **4. Pathological Process:** - Initial inflammation at the entheses (ligament-bone junctions) - Inflammation extends to involve adjacent bone - Healing response forms NEW BONE (syndesmophytes) - Progressive new bone formation eventually FUSES vertebrae - Fusion is irreversible — prevention is critical **Risk Factors:** - Family history of AS or spondyloarthropathies - HLA-B27 positive status - Male sex (2-3x risk) - Age 17-45 at onset - Inflammatory bowel disease - Psoriasis - History of acute uveitis - Northern European or Native American ancestry

## Treatment Has Been Revolutionized in the Past 25 Years The introduction of biologic medications in the early 2000s has transformed AS from a progressively disabling disease to one that is largely controllable. **Treatment Pillars:** **1. Exercise (The Cornerstone — Don't Skip This):** - **Daily exercise is essential** — possibly the single most important non-pharmacologic intervention - **Spinal mobility exercises** — neck rotation, side bending, extension - **Stretching program** — focuses on chest, hip flexors, hamstrings - **Core strengthening** — supports spine - **Aerobic exercise** — swimming is ideal (water buoyancy helps) - **Posture training** — prevents progressive deformity - Studies show exercise reduces pain AND slows radiographic progression **2. Medications:** *First-Line: NSAIDs* - Highly effective for AS pain (more effective than for mechanical back pain) - Continuous use (vs as-needed) may slow progression - Naproxen, ibuprofen, indomethacin, celecoxib - 70-80% have significant response *Second-Line: Biologics (For Inadequate NSAID Response)* **TNF Inhibitors:** - Adalimumab (Humira), Etanercept (Enbrel), Infliximab (Remicade), Golimumab (Simponi), Certolizumab (Cimzia) - 70-80% achieve significant improvement - Slow radiographic progression - Most effective for axial AND peripheral disease **IL-17 Inhibitors:** - Secukinumab (Cosentyx), Ixekizumab (Taltz) - Similar efficacy to TNF inhibitors - Useful when TNF inhibitors fail - Particularly good for skin manifestations **JAK Inhibitors:** - Tofacitinib (Xeljanz), Upadacitinib (Rinvoq) - Oral medication option (vs injection) - Newer option *Other Medications:* - Sulfasalazine — for peripheral joint involvement - Methotrexate — for peripheral joint involvement (less effective for spinal disease) - Local corticosteroid injections — for specific painful joints **3. Physical and Occupational Therapy:** - Postural assessment and correction - Workplace modifications - Home exercise programs - Hydrotherapy (pool exercises) particularly beneficial **4. Lifestyle Modifications:** - **STOP SMOKING** — major impact on disease progression - **Maintain healthy weight** - **Regular physical activity** - **Sleep on a firm mattress with proper neck support** - **Avoid prolonged static positions** - **Cardiovascular health** — increased CV risk requires monitoring **5. Surgery (Rare):** - **Hip replacement** — for severe hip involvement - **Spinal osteotomy** — rare procedure for severe deformity correction **Treatment Goals:** - Pain control - Maintain spinal mobility - Prevent progressive deformity - Treat extra-articular manifestations - Address comorbidities (cardiovascular, mental health) - Improve quality of life **Treatment Outcomes with Modern Care:** - 70-80% achieve significant disease control with biologics - Most patients can maintain near-normal function - Severe disability now uncommon with proper treatment - Progression of fusion can be substantially slowed