Key Facts

Enteropathic arthritis is part of the spondyloarthritis family. Managing the arthritis requires collaboration between rheumatology and gastroenterology.

Epidemiology

• Peripheral arthritis: 10-20% of IBD patients
• Axial disease: 5-10% of IBD patients
• Sacroiliitis (asymptomatic): up to 20-30% on MRI
• More common in Crohn's (especially colonic) than UC
• Can precede IBD diagnosis in some cases

Aetiology

• Shared genetic susceptibility: IL-23R, CARD15/NOD2 (Crohn's), HLA-B27 (axial)
• Gut inflammation → increased intestinal permeability → translocation of bacterial products → systemic immune activation
• Gut-joint axis: shared homing molecules on lymphocytes

Pathophysiology

• IL-23/IL-17 pathway dysregulation (common to spondyloarthropathies and IBD)
• Activated gut-derived T cells and macrophages traffic to joints
• Mucosal inflammation leads to systemic cytokine release (TNF-α, IL-6)
• Enthesitis is a feature, as with other spondyloarthropathies

Type 1 Peripheral (Pauciarticular)

• <5 joints, typically large joints (knee, ankle, hip, elbow)
• Parallels gut disease activity: flares with IBD flares
• Self-limiting: episodes last weeks to months; non-erosive
• Associated with other extra-intestinal manifestations (erythema nodosum, pyoderma gangrenosum, uveitis)

Type 2 Peripheral (Polyarticular)

• ≥5 joints, often small joints (MCP, PIP)
• Independent of gut disease activity: chronic course
• May persist despite bowel remission
• Can be erosive

Axial Disease

• Sacroiliitis and/or spondylitis
• Independent of gut disease activity
• Inflammatory back pain pattern (as per AS)
• May be symmetric or asymmetric sacroiliitis
• Similar progression to AS in some patients

Other Extra-Intestinal Manifestations

• Erythema nodosum, pyoderma gangrenosum
• Anterior uveitis
• Primary sclerosing cholangitis (UC)

Red Flags

• New arthritis symptoms in IBD patient → screen for infection (joint aspiration if monoarthritis)
• Inflammatory back pain → MRI SIJ
• Eye symptoms → urgent ophthalmology

Bloods

• ESR/CRP: elevated (may reflect bowel or joint inflammation)
• FBC: anaemia (chronic disease, iron deficiency from IBD)
• RF, anti-CCP: negative (distinguishes from RA)
• HLA-B27: positive in 50-70% with axial disease
• LFTs: baseline (PSC screening, DMARD monitoring)
• Calprotectin: faecal calprotectin if IBD not yet diagnosed

Imaging

• X-ray: usually normal in type 1; erosive changes possible in type 2
• MRI SIJ/spine: if axial symptoms; sacroiliitis, spondylitis
• Ultrasound: synovitis, enthesitis

Joint Aspiration

• If monoarthritis: exclude septic arthritis and crystal arthropathy

Endoscopy

• If IBD not yet diagnosed but enteropathic arthritis suspected → colonoscopy with biopsies

Type 1 Peripheral

• Treat underlying IBD: often resolves the arthritis
• Simple analgesia: paracetamol
• NSAIDs: use cautiously (may exacerbate IBD); short courses of COX-2 selective (etoricoxib) may be safer
• Intra-articular corticosteroid: for individual joints
• Sulfasalazine: particularly for UC + peripheral arthritis

Type 2 Peripheral

• Sulfasalazine 500mg-1g BD: first-line DMARD
• Methotrexate 15-25mg weekly: if sulfasalazine insufficient
• Anti-TNF (infliximab, adalimumab): for refractory disease; treats both IBD and arthritis

Axial Disease

• Physiotherapy: essential (as per AS management)
• NSAIDs: cautious use; COX-2 selective preferred
• Anti-TNF: first-line biologic for axial disease not responding to NSAIDs (infliximab preferred if concomitant active IBD)
• IL-17 inhibitors: effective for axial disease BUT may worsen IBD (secukinumab associated with IBD flares)

General Principles

• Avoid NSAIDs long-term in IBD: risk of disease flare; use lowest dose for shortest time
• Shared care: rheumatology + gastroenterology MDT approach
• Anti-TNF therapy is ideal as it treats both conditions simultaneously

Referral Criteria

• IBD patient with persistent joint symptoms → rheumatology
• Arthritis preceding bowel symptoms → gastroenterology (investigate for subclinical IBD)
• Axial disease or biologic therapy needed → tertiary centre

• Type 1: self-limiting; parallels IBD; good prognosis
• Type 2: chronic; may cause joint damage; independent of IBD activity
• Axial disease: similar prognosis to AS in severe cases
• Anti-TNF therapy: excellent outcomes for both gut and joint disease
• Overall: less destructive than RA in most patients; early treatment important for type 2 and axial disease

Enteropathic Arthritis Classification

Extra-Intestinal Manifestations of IBD