Rheumatoid Arthritis – High‑Yield Study Guide for Medical Students

Definition

Rheumatoid arthritis (RA) is a chronic, systemic, autoimmune inflammatory polyarthritis characterized by persistent, symmetric inflammation of synovial joints leading to cartilage destruction, bone erosions, and progressive deformity, with potential extra‑articular organ involvement.

Epidemiology

RA is one of the most common autoimmune diseases and an important cause of chronic disability:

Global prevalence ≈ 0.5–1% of the population.
Peak onset: 30–60 years, but can occur at any age.
Sex: female predominance (~3:1), though the sex difference narrows with age.
More common in smokers and in individuals with a family history of RA or other autoimmune disease.
Substantial impact on work participation and functional limitations; work-related disability is often quantified using instruments such as the Workplace Activity Limitations Scale (WALS) in inflammatory arthritis populations.[3](https://pubmed.ncbi.nlm.nih.gov/41822338/)

Pathophysiology

RA results from a complex interaction of genetics, environment, and immune dysregulation leading to chronic synovitis.

Genetic and Environmental Factors

Genetics: Strong association with HLA-DRB1 alleles ("shared epitope"), particularly HLA-DR4; additional non-HLA risk loci (e.g., PTPN22, STAT4).
Environmental triggers: Cigarette smoking (strongest modifiable risk factor), periodontitis, silica exposure, and potentially microbiome alterations; these promote citrullination of proteins and break immune tolerance.

Autoimmunity and Synovial Inflammation

Loss of tolerance: B and T cells target citrullinated proteins, generating autoantibodies such as rheumatoid factor (RF) and anti–cyclic citrullinated peptide (anti‑CCP/ACPA).
Synovial pannus formation: Activated T cells, B cells, macrophages, fibroblast-like synoviocytes (FLS), and endothelial cells create a hyperplastic synovial tissue (pannus) that invades cartilage and bone.
Cytokine milieu: TNF-α, IL-6, IL-1, and GM-CSF drive inflammation; RANKL promotes osteoclastogenesis and bone erosion.[7](https://europepmc.org/article/MED/41782910)

Joint Damage and Extra‑Articular Disease

Cartilage destruction: Proteases from synoviocytes and inflammatory cells degrade cartilage matrix.
Bone erosion: Osteoclast activation at the bone–pannus interface leads to marginal erosions.
Systemic inflammation: Chronic cytokine elevation contributes to anemia of chronic disease, accelerated atherosclerosis, and involvement of serosal surfaces such as the pericardium.[8](https://europepmc.org/article/MED/41835349)

Clinical Presentation

Articular Manifestations

RA typically presents as a chronic, symmetric, inflammatory polyarthritis:

Onset: Insidious over weeks to months (less commonly acute).
Pattern: Symmetric small-joint involvement: metacarpophalangeal (MCP), proximal interphalangeal (PIP), wrists, metatarsophalangeal (MTP) joints; may later involve large joints (knees, ankles, shoulders, elbows, hips).
Inflammatory pain: Morning stiffness > 30–60 minutes that improves with activity; worsening after rest.
Swelling: "Boggy" synovial swelling, warmth, decreased range of motion.
Chronic deformities:
- Ulnar deviation of fingers at MCP joints.
- Radial deviation of the wrist.
- Boutonnière deformity (PIP flexion with DIP hyperextension).
- Swan neck deformity (PIP hyperextension with DIP flexion).
- Hammer toes and MTP subluxation in the feet.

Extra‑Articular Manifestations

More common in seropositive (RF/ACPA-positive) disease and in patients with long-standing or poorly controlled RA.

Constitutional: Fatigue, low-grade fever, weight loss, malaise.
Rheumatoid nodules: Firm, subcutaneous nodules over extensor surfaces and pressure points (e.g., olecranon).
Ocular: Keratoconjunctivitis sicca (secondary Sjögren), episcleritis, scleritis.
Pulmonary: Pleural effusions, interstitial lung disease, rheumatoid nodules.
Cardiac: Pericarditis and other forms of autoimmune pericardial disease are recognized extra‑articular manifestations and may be detected via advanced imaging.[8](https://europepmc.org/article/MED/41835349)
Hematologic: Anemia of chronic disease, thrombocytosis, Felty syndrome (RA + splenomegaly + neutropenia).
Neurologic: Peripheral neuropathy, cervical spine involvement (atlantoaxial subluxation) with potential cord compression.
Vasculitis: Small- and medium-vessel vasculitis causing ulcers, mononeuritis multiplex (rare in modern treatment era).

Differential Diagnosis

Osteoarthritis: Non-inflammatory, asymmetric, DIP involvement common, brief or no morning stiffness.
Psoriatic arthritis: Dactylitis, nail pitting, psoriasis skin lesions, often asymmetric, enthesitis.
SLE and other CTDs: Nonerosive arthritis, systemic features, autoantibody profile.
Viral arthritis: Parvovirus B19, hepatitis B/C, Chikungunya; typically acute, self-limited.
Crystal arthropathies: Gout, CPPD; often mono‑ or oligoarticular with acute flares.
Seronegative spondyloarthropathies: Axial involvement, sacroiliitis, HLA‑B27 association.
Infiltrative/hematologic disease: Rarely, AL amyloidosis–associated arthritis can mimic RA with chronic inflammatory arthritis; suspicion is warranted in atypical presentations or associated plasma cell dyscrasia.[6](https://europepmc.org/article/MED/41786614)

Diagnosis

Diagnosis is clinical, supported by serology and imaging, using the 2010 ACR/EULAR classification criteria for RA.

2010 ACR/EULAR Classification Criteria (Simplified)

These criteria apply to patients with at least one joint with definite clinical synovitis not better explained by another disease. A score ≥ 6/10 classifies RA.

Joint involvement (0–5 points):
- 1 large joint: 0 points.
- 2–10 large joints: 1 point.
- 1–3 small joints (with or without large joints): 2 points.
- 4–10 small joints (with or without large joints): 3 points.
- >10 joints (at least 1 small): 5 points.
Serology (0–3 points):
- Negative RF and negative ACPA: 0 points.
- Low-positive RF or ACPA: 2 points.
- High-positive RF or ACPA: 3 points.
Acute-phase reactants (0–1 point):
- Normal CRP and ESR: 0 points.
- Abnormal CRP or ESR: 1 point.
Duration of symptoms (0–1 point):
- <6 weeks: 0 points.
- ≥6 weeks: 1 point.

Laboratory Evaluation

Autoantibodies:
- Rheumatoid factor (RF): IgM antibody against Fc portion of IgG; sensitivity ≈ 70–80%, specificity moderate; also seen in other diseases.
- Anti-CCP (ACPA): Similar sensitivity to RF but higher specificity (~95%); associated with more aggressive, erosive disease.
Inflammatory markers: Elevated ESR and CRP correlate with disease activity.
Baseline labs: CBC (anemia of chronic disease, thrombocytosis), CMP (renal/hepatic function), lipid profile (for CVD risk), and screening prior to DMARDs (HBV, HCV, HIV, TB).
Joint aspiration: In selected cases to exclude infection or crystal disease; inflammatory synovial fluid with WBC 2,000–50,000/µL, predominantly neutrophils.

Imaging

Plain radiographs: Early: soft tissue swelling, juxta-articular osteopenia. Later: joint-space narrowing, marginal erosions, subluxations.
Ultrasound: Sensitive for synovitis, power Doppler signal (active inflammation), and erosions; useful in early disease and monitoring.
MRI: Detects synovitis, bone marrow edema, and early erosions before they appear on X-ray.

Management

Treatment aims to achieve remission or low disease activity using a treat‑to‑target strategy, prevent structural damage, optimize function, and address comorbidities.

General Principles

Early diagnosis and prompt initiation of disease‑modifying antirheumatic drugs (DMARDs) are critical to prevent irreversible joint damage.
Treat-to-target: Regular assessment with standardized disease activity scores (e.g., DAS28, CDAI) to adjust therapy aiming for remission or low activity.
Multidisciplinary care: Rheumatologist, primary care, physical and occupational therapy, and patient education about self‑management and workplace adaptations.[3](https://pubmed.ncbi.nlm.nih.gov/41822338/)

Non‑Pharmacologic Therapy

Patient education and shared decision‑making regarding treatment options and long-term course.
Exercise and physical therapy to maintain strength, range of motion, and cardiovascular health.
Occupational therapy, joint protection strategies, assistive devices, and ergonomic modifications at work.
Smoking cessation and optimization of weight and cardiovascular risk factors.

Pharmacologic Therapy

1. NSAIDs and Analgesics

Provide symptomatic relief of pain and stiffness but do not alter disease course.
Used as adjuncts, especially at initial presentation or during flares, with attention to GI, renal, and cardiovascular risks.

2. Glucocorticoids

Effective, rapid anti‑inflammatory agents used as "bridge therapy" when initiating or adjusting DMARDs.
Common regimens: low‑dose oral prednisone (e.g., 5–10 mg daily) short term; intra‑articular injections for mono-/oligoarticular flares.
Long‑term use is limited by adverse effects (osteoporosis, infection, diabetes, hypertension); contemporary primary care practice increasingly emphasizes cautious, time‑limited prednisone prescribing in RA.[1](https://pubmed.ncbi.nlm.nih.gov/41844309/)

3. Conventional Synthetic DMARDs (csDMARDs)

Methotrexate (MTX) – first-line anchor drug:
- Typical starting dose 7.5–15 mg once weekly (oral or subcutaneous), titrated up to 20–25 mg weekly as tolerated.
- Give folic acid (e.g., 1 mg daily or 5 mg weekly) to reduce toxicity.
- Monitor CBC, LFTs, and renal function; counsel regarding teratogenicity, alcohol use, and infection risk.
Leflunomide: Alternative to MTX or in combination; hepatotoxicity and teratogenicity are concerns.
Sulfasalazine: Often used in combination regimens; monitor for cytopenias and hypersensitivity.
Hydroxychloroquine: Mild DMARD, useful in early or mild disease and in combination; requires periodic ophthalmologic monitoring.

4. Biologic DMARDs (bDMARDs)

Indicated for moderate-to-severe RA with inadequate response to csDMARDs, particularly methotrexate.
TNF inhibitors (TNFi): Etanercept, infliximab, adalimumab, golimumab, certolizumab.
- Often used in combination with MTX.
- Up to 40% of patients may have primary or secondary failure to a first TNFi.[7](https://europepmc.org/article/MED/41782910)
- When the first TNFi fails, expert consensus supports stratifying the next step (cycling to another TNFi vs. switching to a different mechanism of action) based on predictors such as presence of primary vs. secondary nonresponse, comorbidities, and patient preference.[7](https://europepmc.org/article/MED/41782910)
Non-TNF biologics:
- Abatacept (T-cell co‑stimulation modulator).
- Rituximab (anti‑CD20 B‑cell depleting antibody).
- Tocilizumab, sarilumab (IL‑6 receptor inhibitors).
Before initiating bDMARDs, screen for TB, hepatitis B/C, and update immunizations.

5. Targeted Synthetic DMARDs (tsDMARDs)

JAK inhibitors: Tofacitinib, baricitinib, upadacitinib, filgotinib.
Oral agents targeting Janus kinase pathways, effective in csDMARD- and bDMARD-insufficient response.
Risks include infections (including herpes zoster), cytopenias, lipid increases, and potential cardiovascular and thrombotic events; require careful risk stratification and monitoring.

Monitoring and Treat‑to‑Target Strategy

Assess disease activity regularly (every 1–3 months in active disease) using DAS28 or similar scores.
Adjust DMARD regimen until remission or low disease activity is achieved and maintained.
Monitor for drug toxicity: CBC, LFTs, creatinine, lipids, and specific safety parameters depending on agent.
Bone health: Assess fracture risk, consider calcium/vitamin D and bisphosphonates, especially with glucocorticoid exposure.

Surgical Management

Indications include severe pain, advanced joint destruction, instability, or tendon rupture despite optimized medical therapy.
Procedures: Synovectomy (less common with modern DMARDs), tendon repair, joint arthroplasty (e.g., hip, knee, MCP), and cervical spine stabilization for atlantoaxial instability.

Key Clinical Pearls

Think RA in any patient with persistent (>6 weeks), symmetric inflammatory polyarthritis of small joints, especially with prolonged morning stiffness.
Anti‑CCP antibodies are more specific than RF and predict more aggressive, erosive disease.
Early, aggressive DMARD therapy—especially methotrexate-based—within the first 3–6 months (“window of opportunity”) markedly improves long-term outcomes.
Glucocorticoids are effective short-term but should be minimized due to cumulative toxicity; use the lowest effective dose for the shortest duration and plan for taper once DMARDs take effect.[1](https://pubmed.ncbi.nlm.nih.gov/41844309/)
TNF inhibitor failure is common and should prompt a structured reassessment; switching to a different mechanism of action is often preferable in primary nonresponders.[7](https://europepmc.org/article/MED/41782910)
Always consider RA as a systemic disease: screen for extra‑articular manifestations such as pericarditis, interstitial lung disease, vasculitis, and hematologic complications.[8](https://europepmc.org/article/MED/41835349)
AL amyloidosis and other plasma cell dyscrasias can mimic RA with chronic inflammatory arthritis; atypical features, poor response to standard therapy, or systemic red flags should trigger reconsideration of the diagnosis.[6](https://europepmc.org/article/MED/41786614)
Work disability is a major consequence of RA; incorporating tools like WALS and early occupational interventions can significantly improve vocational outcomes.[3](https://pubmed.ncbi.nlm.nih.gov/41822338/)