What are the different types of arthritis and their respective treatments?

Types of Arthritis and Differentials

Major Categories of Arthritis

Arthritis encompasses multiple distinct disease entities that require differentiation for appropriate management and prognostication.

Juvenile Idiopathic Arthritis (JIA)

JIA is classified into distinct treatment groups based on joint involvement patterns, not just ILAR categories, which guides therapeutic decision-making. 1

Clinical Phenotypes:

• Oligoarthritis (≤4 joints): Includes persistent oligoarthritis, and patients with psoriatic arthritis, enthesitis-related arthritis, or undifferentiated arthritis affecting 4 or fewer joints throughout disease history 1

• Polyarthritis (≥5 joints): Encompasses extended oligoarthritis, RF-negative polyarthritis, RF-positive polyarthritis, plus psoriatic, enthesitis-related, and undifferentiated arthritis with 5 or more joints ever involved 1

• Systemic arthritis with active systemic features: Characterized by active fever with or without other systemic manifestations (rash, lymphadenopathy, hepatosplenomegaly, serositis) but without active arthritis 1

• Systemic arthritis with active arthritis: Active joint inflammation without concurrent systemic features 1

• Active sacroiliac arthritis: Clinical and imaging-confirmed sacroiliitis, predominantly in enthesitis-related and psoriatic arthritis 1

Diagnostic Criteria:

• Arthritis (joint swelling or limitation with pain/tenderness) persisting ≥6 weeks in patients <16 years old, with exclusion of alternative diagnoses 2
• Laboratory evaluation should include CBC with differential, ESR, CRP, ANA, RF, liver function tests, and albumin 2
• Ultrasound and MRI are superior to clinical examination for detecting joint inflammation 2

Rheumatoid Arthritis (RA)

RA is a systemic inflammatory disease requiring early aggressive treatment with disease-modifying agents to prevent irreversible joint destruction and reduce mortality. 1

Clinical Features:

• Symmetrical polyarthritis affecting small joints of hands and feet, with potential for axial and appendicular joint involvement 1
• Morning stiffness lasting ≥1 hour 1
• Extra-articular manifestations (subcutaneous nodules, interstitial lung disease, vasculitis, inflammatory eye disease) indicate severe disease 1
• Life expectancy reduced by 3-5 years, particularly with extra-articular disease 1

Diagnostic Markers:

• Anti-citrullinated protein antibody (ACPA): 90% specificity, 60% sensitivity 1
• Rheumatoid factor: 70% specificity, comparable sensitivity to ACPA (increases to 80% with prolonged disease) 1
• Elevated CRP is the most clinically useful biomarker 1

Psoriatic Arthritis (PsA)

PsA requires multidimensional assessment across multiple disease domains (arthritis, enthesitis, dactylitis, skin/nail disease, axial involvement) to guide domain-specific treatment. 1, 3

Classification:

• Arthritis with psoriasis, OR arthritis with ≥2 of: dactylitis, nail pitting/onycholysis, or first-degree relative with psoriasis 2
• Accounts for approximately 20% of early arthritis clinic referrals 3

Disease Assessment:

• Treatment targets are remission/inactive disease or low/minimal disease activity 1
• Disease Activity index for PSoriatic Arthritis (DAPSA) and Minimal Disease Activity (MDA) are recommended assessment tools 1

Spondyloarthritis (SpA)

SpA encompasses axial and peripheral forms requiring treat-to-target strategies with remission or low disease activity as primary goals. 1

Enthesitis-Related Arthritis:

• Diagnosed by arthritis and enthesitis, OR arthritis/enthesitis with ≥2 of: sacroiliac tenderness/inflammatory back pain, HLA-B27 positivity, family history of HLA-B27-associated disease, anterior uveitis, or male onset >6 years 2

Assessment Tools:

• Ankylosing Spondylitis Disease Activity Score (ASDAS) for axial SpA 1
• MRI particularly valuable for detecting temporomandibular joint and axial inflammation 2

Osteoarthritis (OA)

OA is characterized by cartilage destruction with local symptoms, cool bony joints, and arthralgia worsening with weight-bearing, typically in patients >60 years. 4

Subtypes:

• Primary generalized: Cartilage narrowing with marginal osteophytes without erosions, predominantly affecting distal interphalangeal joints and first carpometacarpal joint 5
• Secondary: Cartilage narrowing in regions of mechanical stress 5
• Erosive osteoarthritis: Affects proximal and distal interphalangeal joints, evolves to bony fusion in 12-15% of cases 5

Critical Differentials to Exclude

Infectious Arthritis

• Bacterial, viral, fungal, and mycobacterial causes must be ruled out 2

Malignancy

• Leukemia and lymphoma must be excluded, particularly in systemic presentations 2

Other Rheumatic Diseases

• Systemic lupus erythematosus (SLE) and vasculitis require exclusion 2

Reiter's Disease

• Differs from psoriatic arthritis by predominant lower limb involvement (especially feet) with relative hand/wrist sparing 5

Multicentric Reticulohistiocytosis

• Rare disorder with polyarthritis preceding nodular cutaneous eruptions, strikingly symmetrical well-circumscribed erosions with disproportionately mild osteoporosis 5

Progressive Systemic Sclerosis

• Characterized by soft tissue atrophy, dystrophic calcifications, joint deformities, and terminal phalangeal tuft resorption 5

Key Diagnostic Pitfalls

Do not rely solely on ILAR classification categories for treatment decisions in JIA, as clinical phenotypes better reflect disease heterogeneity and guide therapy. 1

Avoid delaying disease-modifying therapy in RA—early aggressive treatment prevents irreversible joint destruction and reduces long-term disability and mortality. 1, 6

In systemic JIA, elevated ferritin with decreased glycosylated ferritin supports diagnosis. 2

Conventional radiography may be normal in early disease; ultrasound and MRI are superior for detecting inflammation. 2