Enthesitis-related arthritis

Australian clinical guidelines for enthesitis-related arthritis (ERA): HLA-B27, sacroiliitis, TNF inhibitor therapy, and transition to ankylosing spondylitis.

Introduction and Overview

Enthesitis-related arthritis (ERA) is a subtype of juvenile idiopathic arthritis characterised by arthritis and/or enthesitis in a child under 16 years of age, occurring predominantly in older males with HLA-B27 positivity. ERA accounts for approximately 10–15% of all JIA cases and is now understood as the paediatric manifestation of the spondyloarthritis (SpA) family of diseases, sharing pathogenesis, genetic associations, and treatment responses with ankylosing spondylitis (AS) and non-radiographic axial SpA in adults. ERA is distinguished by sacroiliac joint and spinal involvement (axial disease), enthesitis at characteristic sites, and a risk of transitioning to adult ankylosing spondylitis. Unlike most other JIA subtypes, ERA predominantly affects males and is strongly HLA-B27 associated.

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Australian Context: ERA is managed in Australian paediatric rheumatology and adult rheumatology centres with NSAIDs as first-line therapy. TNF inhibitors (etanercept, adalimumab) are PBS-listed for ERA refractory to NSAIDs. Sacroiliitis and axial disease require MRI for early detection, as X-ray changes are late in adolescents. Approximately 50% of ERA patients will progress to ankylosing spondylitis in adulthood. Acute anterior uveitis (symptomatic, unlike JIA uveitis) occurs in HLA-B27-positive ERA and requires prompt ophthalmological review.

Feature	ERA	Other JIA Subtypes
Sex predominance	Male (M:F ~7:1)	Female predominance in most subtypes
Age of onset	Older children and adolescents (typically >8 years)	Variable; oligoarticular peaks at 1–4 years
HLA-B27	Positive in ~80–90%	Not a feature
Enthesitis	Defining feature — Achilles, plantar fascia, tibial tuberosity, patella	Absent (except psoriatic JIA occasionally)
Axial disease	Sacroiliitis, spondylitis — may develop over time	Absent
Uveitis	Acute anterior uveitis — symptomatic (red, painful eye)	Chronic asymptomatic in oligoarticular/ANA+
Adult equivalent	Ankylosing spondylitis / axial SpA	Adult-onset RA, Still disease (sJIA)

Pathophysiology

ERA shares the pathogenesis of the spondyloarthritis family, driven by HLA-B27-associated immune dysregulation, IL-17/IL-23 axis activation, and preferential inflammation at entheses (tendon and ligament insertion sites into bone) rather than synovium alone.

Immunological Mechanisms

HLA-B27 association — present in ~80–90% of ERA; HLA-B27 misfolding activates the unfolded protein response (UPR), triggering IL-23 and innate immune activation; exact mechanism linking HLA-B27 to enthesitis is incompletely understood
IL-17/IL-23 axis — central cytokines in SpA pathogenesis; IL-23 drives Th17 cell differentiation producing IL-17, which causes entheseal inflammation and new bone formation; IL-17 inhibitors (secukinumab) are highly effective in adult AS
Entheseal inflammation — entheses are rich in innate immune cells (macrophages, innate lymphoid cells) particularly vulnerable to biomechanical stress; inflammation at entheses drives periostitis, bone erosion, and ultimately syndesmophyte formation
TNF-α — drives synovitis and enthesitis in ERA; TNF inhibitors are highly effective for both peripheral and axial disease

Disease Spectrum

Peripheral ERA — peripheral enthesitis and asymmetric lower limb oligoarthritis predominate in early childhood-onset ERA; sacroiliitis may not be apparent clinically or radiologically initially
Axial ERA — sacroiliac and spinal involvement; MRI sacroiliac joints demonstrates bone marrow oedema before X-ray changes; sacroiliitis may evolve to ankylosing spondylitis in adulthood

Clinical Presentation

ERA presents with a combination of peripheral arthritis, enthesitis, and axial involvement in an older male child or adolescent. Enthesitis and inflammatory back pain are the hallmark features that differentiate ERA from other JIA subtypes.

Enthesitis

Achilles tendon insertion — most common site; posterior heel pain and tenderness; swelling at the calcaneal insertion; pain worsened by activity and passive dorsiflexion
Plantar fascia insertion — plantar heel pain; often bilateral; tenderness over medial calcaneal tuberosity
Tibial tuberosity (Osgood-Schlatter-like) — tenderness at patellar tendon insertion; distinguishable from Osgood-Schlatter by age, sex, and co-existing arthritis/enthesitis at other sites
Patellar insertion — superior and inferior pole of patella; anterior knee pain distinct from patellofemoral pain syndrome
Costovertebral junctions — chest wall pain; may be misattributed to musculoskeletal strain

Peripheral Arthritis

Asymmetric oligoarthritis — predominantly lower limb; hips, knees, and ankles most commonly involved; hip arthritis is a feature of ERA not typical in oligoarticular JIA
Hip arthritis — groin pain with limited internal rotation; one of the characteristic joint patterns in ERA; associated with worse long-term functional outcome
Dactylitis — sausage toe or finger (diffuse digit swelling due to combined flexor tenosynovitis and MTP/PIP arthritis); less common than in psoriatic JIA but occurs in ERA

Axial Disease

Inflammatory back pain — insidious onset, improves with activity (unlike mechanical back pain which worsens); morning stiffness >30 minutes; nocturnal pain causing wakening; buttock pain alternating sides (sacroiliitis)
Limited spinal mobility — reduced lumbar forward flexion (modified Schober test), reduced chest expansion; may be absent early in disease
Sacroiliac joint tenderness — FABER and Gaenslen tests positive; direct sacroiliac compression tenderness

Extra-Articular Features

Acute anterior uveitis (AAU) — unilateral, red, painful eye with photophobia; acutely symptomatic (unlike the asymptomatic chronic uveitis of oligoarticular JIA); HLA-B27 associated; self-limited but recurrent; requires prompt ophthalmological assessment
Inflammatory bowel disease association — ERA and SpA are associated with subclinical bowel inflammation; Crohn disease and ulcerative colitis increase ERA risk and share pathogenesis
Psoriasis — presence of psoriasis with arthritis and HLA-B27 positivity suggests psoriatic JIA/SpA overlap

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Hip Arthritis in ERA: Hip involvement in ERA carries a worse prognosis than hip disease in other JIA subtypes and may cause rapid hip destruction if undertreated. Any ERA patient with hip pain and limited internal rotation requires urgent paediatric rheumatology review and hip MRI. Early biologic therapy is warranted for active hip arthritis in ERA.

Investigations

ERA is a clinical diagnosis based on ILAR criteria (arthritis and/or enthesitis plus two or more of: sacroiliac tenderness, inflammatory spinal pain, HLA-B27, family history of SpA, AAU, onset in a male >6 years). Investigations confirm the diagnosis and exclude mimics.

Essential
HLA-B27
Positive in ~80–90% of ERA. Confirms spondyloarthritis spectrum diagnosis when combined with clinical features. HLA-B27 negative ERA does exist. A positive result strengthens the diagnosis, guides prognosis (risk of axial progression and AAU), and supports NSAID-first treatment strategy. Not sufficient alone for diagnosis.
Essential
FBC, ESR, CRP
Inflammatory markers elevated in active ERA. Normal ESR and CRP do not exclude ERA — unlike RA, inflammatory markers may be disproportionately low relative to disease activity. Anaemia of chronic disease in severe or longstanding disease.
Essential
ANA and RF
Negative in ERA by definition. Positive RF excludes ERA and suggests RF-positive polyarticular JIA. Positive ANA in a child with enthesitis and HLA-B27 should prompt reconsideration of the diagnosis. Anti-CCP is also negative in ERA.
Essential
MRI sacroiliac joints (with STIR sequence)
The investigation of choice for early sacroiliitis in ERA. X-rays are normal until structural damage has occurred (late finding). MRI STIR sequence identifies bone marrow oedema (active sacroiliitis) and structural lesions (sclerosis, erosions, ankylosis). Mandatory in any ERA patient with buttock pain, inflammatory back pain, or clinical sacroiliac joint tenderness. Also used to monitor treatment response in axial disease.
Recommended
Pelvic X-ray (AP view)
Baseline for structural damage assessment. Usually normal in early/adolescent ERA. Joint space narrowing, sclerosis, erosions, and bridging indicate established sacroiliitis. X-ray changes confirm Grade II+ sacroiliitis (per NY criteria) when present but are insensitive for early disease. Spinal X-ray (lateral lumbar) for syndesmophytes in longstanding disease.
Recommended
Musculoskeletal ultrasound
Useful for confirming and quantifying enthesitis at Achilles, plantar fascia, and patellar insertions. Doppler signal confirms active inflammation. Guides intra-entheseal corticosteroid injection if needed (peritendinous injection; never directly into Achilles tendon).

Risk Stratification

ERA severity is assessed across peripheral joint activity, enthesitis burden, and axial disease. Poor prognostic features include hip involvement, axial progression, and inadequate NSAID response.

MILD

Peripheral Only, NSAID-Responsive

Peripheral enthesitis and few joints; responds to NSAIDs; no axial disease; no hip involvement

Regular NSAIDs (naproxen or indomethacin); physiotherapy; intra-articular/peritendinous injection if needed

MODERATE

Peripheral, NSAID-Insufficient

Multiple joints and enthesitis sites; NSAID-insufficient; early sacroiliitis on MRI; functional limitation

TNF inhibitor (etanercept or adalimumab); NSAID continuation; physiotherapy intensive program

SEVERE

Axial or Hip Disease, Biologic-Refractory

Hip arthritis; established sacroiliitis; active axial disease; TNFi failure; functional impairment

Switch TNFi or IL-17 inhibitor (secukinumab — off-label paediatric); urgent rheumatology review; hip surgery if avascular necrosis

Pharmacological Management

NSAIDs are the cornerstone of ERA therapy and can be sufficient for mild peripheral disease. TNF inhibitors are the primary biologic class for NSAID-refractory ERA, including axial disease, hip involvement, and persistent enthesitis. Methotrexate has limited efficacy for axial and enthesitis-predominant ERA but may help peripheral arthritis.

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NSAIDs (Naproxen / Indomethacin)

Naprosyn® / Indocid® | First-line therapy for ERA

DoseNaproxen: 10–15 mg/kg/day in 2 doses (max 1000 mg/day); Indomethacin: 1–3 mg/kg/day in 3–4 doses (max 150 mg/day) — particularly effective for spinal pain

PBS Status✓ PBS: General benefit

NotesContinuous regular dosing for 4–6 weeks is required to assess NSAID response — as-needed use is insufficient for ERA. Indomethacin is often preferred for inflammatory back pain (more potent than naproxen for spinal disease). NSAIDs may slow radiographic progression in AS (continuous use). Gastroprotection with PPI if prolonged use or GI risk factors. Adequate NSAID response after 3 months is a positive prognostic sign.

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Etanercept

Enbrel® | TNF inhibitor — first-line biologic for ERA

Dose0.4 mg/kg SC weekly (max 25 mg) or 0.8 mg/kg SC fortnightly (max 50 mg)

PBS Status✓ PBS: ERA failing NSAIDs over 3 months; paediatric rheumatologist or rheumatologist initiation; Authority required

NotesFirst-line biologic for peripheral arthritis and enthesitis in ERA. NSAID failure (inadequate response after 3 months of regular NSAIDs) is the PBS requirement for biologic access. Latent TB (IGRA) and HBV screening mandatory. Note: etanercept may be LESS effective than monoclonal TNFi for axial disease (sacroiliitis/spondylitis) in ERA — consider adalimumab for predominantly axial ERA. Common: injection site reactions. Serious: infection, reactivation TB.

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Adalimumab

Humira® | TNF inhibitor — preferred for axial ERA and IBD-associated ERA

Dose20 mg SC fortnightly (<30 kg); 40 mg SC fortnightly (≥30 kg)

PBS Status✓ PBS: ERA failing NSAIDs; paediatric rheumatologist initiation; Authority required

NotesMonoclonal anti-TNF antibody — generally preferred over etanercept for axial ERA (sacroiliitis and spondylitis) based on adult axial SpA evidence. Also effective for IBD-associated ERA and uveitis (unlike etanercept which lacks uveitis efficacy). IGRA and HBV screening before initiation. Combine with MTX if peripheral disease is the main feature (reduces immunogenicity).

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Methotrexate

Various generics | Peripheral disease adjunct

Dose10–15 mg/m²/week SC (preferred) or oral; max 25 mg/week

PBS Status✓ PBS: Polyarticular-course JIA; rheumatologist initiation

NotesLimited efficacy for axial ERA and enthesitis — NOT a substitute for NSAIDs or biologics for axial disease. May be useful as adjunct for peripheral synovitis in ERA if insufficient biologic access. Folic acid 5 mg once weekly. FBC and LFTs monthly for 3 months then 3-monthly. MTX should not be the primary therapy for ERA if axial disease is present.

Directed Therapy

Specific manifestations of ERA require targeted management in addition to systemic therapy.

Enthesitis-Directed Therapy

Intra-articular corticosteroid injection (IAC) — triamcinolone hexacetonide for highly active peripheral joints; under ultrasound guidance for hip and sacroiliac joint; provides short-term joint and enthesitis control while awaiting biologic effect
Peritendinous injection — for Achilles and plantar enthesitis refractory to NSAIDs; ultrasound-guided peritendinous (NOT intratendinous) triamcinolone; NEVER inject directly into the Achilles tendon (risk of rupture)
Orthotics — heel cups and Achilles off-loading footwear for plantar fascia and Achilles enthesitis; reduces mechanical load at affected entheses

Acute Anterior Uveitis Management

Topical prednisolone acetate 1% and cycloplegic (homatropine or cyclopentolate) — first-line for AAU; frequency guided by severity; ophthalmologist directed
Adalimumab preferred over etanercept — for ERA patients with recurrent or severe AAU; etanercept does not prevent uveitis recurrence in SpA
Prompt ophthalmology referral — any HLA-B27-positive child with red, painful eye requires same-day ophthalmology assessment; delay risks posterior synechiae and vision loss

Sacroiliitis and Axial Disease

MRI-guided monitoring — MRI STIR sacroiliac joints at diagnosis and 12–24 monthly if axial disease present; MRI sacroiliac joint response to TNFi at 3–6 months guides biologic continuation
Intra-articular sacroiliac joint injection — CT or fluoroscopy-guided triamcinolone for active sacroiliitis; used when systemic therapy cannot be commenced or is delayed
Physiotherapy — SpA-specific exercise program; core and posterior chain strengthening; spinal flexibility exercises; hydrotherapy; aerobic exercise (cycling, swimming)

Non-Pharmacological Management

Non-pharmacological management is fundamental in ERA and includes a specific exercise program for axial disease, education about disease trajectory, and vocational support for affected adolescents.

Physiotherapy — SpA Exercise Program

Daily exercise is essential — inactivity accelerates spinal stiffness and kyphosis in ERA with axial disease; exercise is as important as medication in preventing deformity
Spinal extension exercises — counteract kyphotic posture; thoracic extension, neck retraction; performed daily ideally in prone
Breathing exercises — thoracic expansion exercises maintain chest expansion; costovertebral joint inflammation limits chest expansion if untreated
Hydrotherapy — warm water reduces entheseal pain and morning stiffness; allows range of motion exercise without joint loading; particularly useful for hip and lower limb enthesitis
Aerobic exercise — cycling and swimming are low-impact activities suitable for ERA; avoid high-impact sports during active enthesitis; return to sport when enthesitis is controlled

Footwear and Orthoses

Cushioned footwear with Achilles heel lift — for Achilles and plantar enthesitis; reduces mechanical stress at calcaneal insertion
Custom orthotics — for flatfoot deformity associated with hindfoot arthritis; podiatry referral
Activity modification — avoid hard surfaces and prolonged standing during active Achilles or plantar enthesitis; return to sport as symptoms resolve with treatment

Psychosocial and School Support

Adolescent-specific support — ERA impacts sport participation, social activities, and identity in adolescent males; peer support and adolescent rheumatology services provide age-appropriate care
School accommodations — modified PE participation during enthesitis flares; elevator access if lower limb disease is severe; formal letter from rheumatology team

Monitoring Parameters

Monitoring in ERA encompasses disease activity assessment (peripheral and axial), enthesitis scoring, imaging for axial progression, and treatment toxicity surveillance.

Parameter	Frequency	Indication
ESR, CRP	Each specialist visit (3–6 monthly)	Disease activity; may be normal despite active ERA
JADAS or BASDAI (adult tool)	Each specialist visit	Standardised disease activity; BASDAI used at transition
Enthesitis score (LEI or MASES)	Each specialist visit	Quantify entheseal burden; guide treatment escalation
Modified Schober test, chest expansion	Each specialist visit	Axial mobility monitoring; detect progressive restriction
MRI sacroiliac joints (STIR)	At diagnosis; every 12–24 months if axial disease; 6 months after biologic commencement	Monitor active and structural sacroiliac disease
FBC, LFTs (on MTX or biologic)	Monthly first 3 months on MTX; 3-monthly; before each biologic infusion	Treatment toxicity
Ophthalmological assessment	Prompt review for any red, painful eye; annual review for HLA-B27 positive ERA	Acute anterior uveitis detection and recurrence monitoring
IGRA and HBV serology	Before each new biologic; annually on biologic	Reactivation screening

When to Refer Urgently

Acute anterior uveitis: Red, painful, photophobic eye in a child with ERA — same-day ophthalmology referral; delay risks synechiae and permanent visual impairment
Hip arthritis in ERA: Rapid groin pain with limited hip internal rotation — urgent rheumatology review; hip MRI; consider early TNFi to prevent avascular necrosis
Cervical spine instability: Neck pain with neurological symptoms — MRI cervical spine before any anaesthetic procedure

Special Populations

Specific clinical considerations apply to ERA patients with particular disease patterns or circumstances.

ERA with IBD (Inflammatory Bowel Disease)

Gut-joint axis — ERA and SpA are associated with gut inflammation; up to 60% of SpA patients have subclinical bowel inflammation on biopsy; 5–10% develop overt IBD
Adalimumab preferred biologic — effective for both ERA and IBD; etanercept is NOT effective for IBD and may worsen gut disease
NSAIDs with caution in IBD — NSAIDs can trigger IBD flares; minimise NSAID dose; consider celecoxib as a less gut-toxic alternative

Transition to Adult Services

~50% of ERA patients will transition to ankylosing spondylitis in adulthood — structured transition to adult rheumatology is essential; adult SpA management (including secukinumab and ixekizumab which are IL-17 inhibitors available for adult AS) extends treatment options
Modified New York criteria for AS — applied at age 18 for classification; transition note must include imaging results, HLA-B27 status, and prior treatment history
Fertility and ERA — TNF inhibitors are generally safe in pregnancy for males with ERA; females transitioning need contraception counselling and biologic safety discussion

ERA vs Reactive Arthritis (ReA)

Reactive arthritis is a post-infectious SpA (post-streptococcal, post-chlamydial, post-enteric) — usually self-limited; HLA-B27 positive in ~50%; may evolve to ERA if it fails to resolve
Distinguishing features — ReA has identifiable preceding infection (urethritis, diarrhoea, respiratory); ERA has insidious onset without preceding infection trigger; ReA usually resolves within 6 months

Aboriginal and Torres Strait Islander Health Considerations

Aboriginal and Torres Strait Islander Health

ERA in Aboriginal and Torres Strait Islander (ATSI) children and adolescents must be distinguished from reactive arthritis following group A streptococcal (GAS) infections, which are highly prevalent in ATSI communities, and from acute rheumatic fever (ARF) with arthritis. Incorrect diagnosis and premature immunosuppression in ARF has serious consequences including risk of ongoing streptococcal infection without secondary prophylaxis.

ARF and Reactive Arthritis Exclusion

Post-streptococcal reactive arthritis (PSRA) and ARF must be excluded before diagnosing ERA in any ATSI child or adolescent with oligoarthritis and enthesitis. ATSI communities have among the highest GAS disease rates globally. Obtain ASO titre, anti-DNase B, throat swab, and ECG in all ATSI children with inflammatory arthritis. ARF arthritis can involve lower limb joints in a distribution resembling ERA. HLA-B27 positivity does not exclude ARF — both conditions can co-exist. If ARF is confirmed, secondary prophylaxis with monthly benzathine penicillin G must be commenced before any immunosuppressive therapy.

TB and Strongyloides Screening Before Biologics

TNF inhibitors are the primary biologic for ERA and have serious reactivation risks in ATSI patients with latent TB and strongyloides. IGRA testing (not TST in BCG-vaccinated children) is mandatory before TNFi initiation. Strongyloides serology must be performed and treated with ivermectin before commencing any immunosuppressive therapy. Hepatitis B surface antigen and anti-HBc testing are also required. ATSI patients with IGRA positivity require prophylactic isoniazid with infectious diseases input before TNFi can be commenced.

Enthesitis Distinguishing from Trauma and Overuse

Enthesitis in ATSI children living in remote communities may be under-recognised or attributed to physical activity and overuse. Inflammatory enthesitis (ERA) characteristically involves multiple simultaneous entheseal sites, is worse with inactivity and morning stiffness, and improves with activity — the opposite of mechanical overuse. Physiotherapy assessment for distinguishing features and rheumatology review is essential. Early correct diagnosis prevents cumulative joint damage from delayed treatment.

Access to Rheumatology and Biologic Therapy

Paediatric and adult rheumatology are capital city services. Telehealth rheumatology is now the standard for ongoing management of ERA in remote ATSI communities. PBS authority prescriptions for TNF inhibitors require specialist initiation — telehealth rheumatology consultations are acceptable for authority applications in most states. Aboriginal Health Workers support medication administration monitoring and recognition of injection site reactions. MRI availability in remote areas is limited — coordinate with regional centres for imaging where possible, or obtain at capital city visits.

Appropriate Use of Medicine and Stewardship

Stewardship in ERA focuses on adequate NSAID trials before biologic escalation, selection of the correct TNF inhibitor for axial versus peripheral disease, avoidance of corticosteroids as long-term therapy, and timely biologic access for hip arthritis and axial disease.

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Common Stewardship Issues in ERA:

Inadequate NSAID trial before biologic escalation: NSAIDs must be taken continuously at full anti-inflammatory doses for at least 3 months before NSAID failure can be declared. As-needed NSAID use is insufficient. Regular indomethacin or naproxen should be trialled continuously first.
Choosing etanercept over adalimumab for axial ERA: Etanercept is less effective than monoclonal TNFi (adalimumab, infliximab) for axial spondyloarthritis. For ERA with sacroiliitis or inflammatory back pain, adalimumab is the preferred TNFi. Etanercept is acceptable for peripheral arthritis and enthesitis-only ERA.
Using methotrexate as sole therapy for axial ERA: MTX has no proven efficacy for axial SpA. Prescribing MTX for ERA with sacroiliitis instead of NSAIDs/TNFi is inappropriate and delays effective treatment.
Delayed biologic therapy for hip arthritis in ERA: Hip involvement in ERA carries high risk of avascular necrosis with corticosteroids and rapid joint destruction without effective treatment. TNFi therapy should not be delayed for hip ERA — early biologic use is warranted.

GP Role in ERA Management

Initial recognition — older male adolescent with inflammatory heel pain, Achilles enthesitis, hip pain, or inflammatory back pain warrants HLA-B27 testing and rheumatology referral
NSAID trial — commence regular naproxen or indomethacin while awaiting rheumatology review; document response duration and adequacy
Monitoring on biologic — FBC, LFTs 3-monthly; IGRA and HBV serology annually; report serious infections; hold biologic during febrile illness
AAU recognition — educate HLA-B27-positive ERA patients that red, painful, photophobic eye requires same-day ophthalmology assessment — not watchful waiting
Immunisation — all vaccinations before biologic initiation; annual influenza vaccine; no live vaccines on biologics

Follow-up and Prevention

ERA requires long-term specialist follow-up given the risk of axial progression, hip involvement, and transition to ankylosing spondylitis. Approximately 50% of ERA patients will develop ankylosing spondylitis in adulthood; early effective treatment reduces this risk and limits structural damage.

Diagnosis

HLA-B27, ESR/CRP, ANA/RF; MRI sacroiliac joints; pelvic X-ray; ophthalmology referral; NSAID (indomethacin or naproxen) at therapeutic dose; physiotherapy referral; ARF exclusion in ATSI; TB and strongyloides screen if ATSI.

Month 1–3

Assess NSAID response; JADAS and enthesitis score; if inadequate response and hip/axial disease — initiate TNFi (adalimumab for axial/uveitis, etanercept for peripheral); IGRA and HBV before biologic.

Month 3–6

MRI response assessment for axial disease; FBC/LFTs; enthesitis score; axial mobility tests; adjust biologic if insufficient response.

Every 6 months (stable)

BASDAI/JADAS; enthesitis score; Schober test and chest expansion; inflammatory markers; FBC/LFTs; annual ophthalmology if HLA-B27 positive; MRI sacroiliac joints every 12–24 months if axial disease.

Transition (age 16–18)

Structured transition to adult rheumatology; summarise HLA-B27 status, MRI results, treatment history; apply modified NY criteria for AS classification; continue biologics through transition; discuss fertility and medication safety in young adults.

References

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Ringold S, et al. 2019 ACR/AF guideline for the treatment of juvenile idiopathic arthritis. Arthritis Care Res. 2019;71(6):717–734.
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Flato B, et al. The influence of HLA-B27 and methotrexate in juvenile idiopathic arthritis with enthesitis-related arthritis. Rheumatology. 2009;48(4):414–417.
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