Systemic inflammatory autoimmune disorder characterized by joint pain, swelling, and synovial destruction.

Risk factors: Genetics (HLA-DR1, HLA-DR4) and environmental trigger (smoking, infection)

Citrullation of type II collagen and vimentin causes production of autoantibodies (anti-CCP).T cells secrete IFN-γ and IL-17, macrophages secrete TNFα, IL-1, IL-6 → synovial cell proliferation → pannusImmune complexes of anti-CCP and anti-RF form immune complexes that activate the complement system.

Symptoms:- Usually ≥5 joints, symmetrical; commonly small joints (MCP PIP, MTP)- Morning stiffness >1h- Flares: Swollen, warm, red painful→ Ulnar deviation, Boutonniere deformity, swan neck deformity, Baker cyst- Fever (IL-1 and IL-6), malaise, muscle weakenss- Rheumatoid nodules in the skin around pressure points (eg, elbow)- ↑ risk of atherosclerosis- ↑ Hepcidin caused ↓ iron absorption → anemia- Interstitial lung disease, pleural effusion

Felty syndrome: Rheumatoid arthritis + Splenomegaly + Granulocytopenia

Diagnosis:- Rheumatoid factor, anti-citrullinated peptide antibody- X-Ray: ↓ bone density, soft tissue swelling, narrowing of joint space, erosions

Treatment:- Disease-modifying anti-rheumatic medications (DMARDs): Methotrexate, hydroxychloroquine, sulfasalazine- Biologicals: Abatacept, rituximab, adalimumab/etanercept/infliximab, anakinra (blocks IL-1)- Acute flairs: NSAIDs, glucocorticoids