🧬 FCPS Paediatrics TOACS · Enthesitis-Related Arthritis (ERA) / Juvenile Spondyloarthritis
📖 Teen with inflammatory back pain · Morning stiffness · Normal X-ray – Approach to Axial SpA (Chapter 197, Nelson's)
📚 paeds.online – Paeds Online
🩺 OBSERVED/INTERACTIVE STATION · CPSP FORMAT · 8 MINUTES · SPONDYLOARTHRITIS / ERA / JUVENILE ANKYLOSING SPONDYLITIS
🦴 Observed Station – “Adolescent male, chronic low back pain, morning stiffness, normal X-ray”
👦🏽 Clinical scenario (displayed & read by candidate):
A 15‑year‑old boy presents with low back pain and morning stiffness for the past 7 months. Pain is worse in the early morning (lasting >45 minutes) and improves with physical activity. He has night pain that awakens him from sleep. There is no history of trauma. Naproxen (NSAID) taken for 10 days resolved symptoms completely, but pain recurred within 4 days after stopping. He also complains of left heel pain (Achilles insertion) and occasional right knee swelling without redness.
General examination: normal posture. Lumbosacral spine X‑ray: normal (no sacroiliitis or syndesmophytes). Ultrasound KUB: normal. Renal function tests, urinalysis: unremarkable. ESR 38 mm/hr, CRP 1.8 mg/dL.
🎯 Task (examiner observed): Formulate the most likely diagnosis (Enthesitis‑related arthritis / Juvenile axial spondyloarthritis). Discuss the concept of “non‑radiographic axial SpA”, justify the need for MRI sacroiliac joints, interpret HLA‑B27 significance, and outline first‑line and biologic treatment according to current guidelines (Nelson's Chapter 197).
A 15‑year‑old boy presents with low back pain and morning stiffness for the past 7 months. Pain is worse in the early morning (lasting >45 minutes) and improves with physical activity. He has night pain that awakens him from sleep. There is no history of trauma. Naproxen (NSAID) taken for 10 days resolved symptoms completely, but pain recurred within 4 days after stopping. He also complains of left heel pain (Achilles insertion) and occasional right knee swelling without redness.
General examination: normal posture. Lumbosacral spine X‑ray: normal (no sacroiliitis or syndesmophytes). Ultrasound KUB: normal. Renal function tests, urinalysis: unremarkable. ESR 38 mm/hr, CRP 1.8 mg/dL.
🎯 Task (examiner observed): Formulate the most likely diagnosis (Enthesitis‑related arthritis / Juvenile axial spondyloarthritis). Discuss the concept of “non‑radiographic axial SpA”, justify the need for MRI sacroiliac joints, interpret HLA‑B27 significance, and outline first‑line and biologic treatment according to current guidelines (Nelson's Chapter 197).
⚠️ Clinical red flags (examiner expects differentiation):
• Mechanical back pain improves with rest, worsens with activity → opposite of this case.
• Inflammatory back pain features: morning stiffness >30 min, improvement with exercise, night pain, good response to NSAIDs.
• Normal X‑ray does NOT exclude early sacroiliitis – MRI shows bone marrow edema before erosions.
• Mechanical back pain improves with rest, worsens with activity → opposite of this case.
• Inflammatory back pain features: morning stiffness >30 min, improvement with exercise, night pain, good response to NSAIDs.
• Normal X‑ray does NOT exclude early sacroiliitis – MRI shows bone marrow edema before erosions.
🔬 Nelson's Table 197.4 & ASAS criteria (Assessment of SpondyloArthritis International Society):
For axial SpA in patients with back pain ≥3 months, age at onset <45 years: MRI+ (active sacroiliitis) + ≥1 SpA feature OR HLA‑B27 + ≥2 SpA features (uveitis, psoriasis, enthesitis, dactylitis, good NSAID response, elevated CRP, family history). This patient meets “good NSAID response” + enthesitis + HLA‑B27 pending.
For axial SpA in patients with back pain ≥3 months, age at onset <45 years: MRI+ (active sacroiliitis) + ≥1 SpA feature OR HLA‑B27 + ≥2 SpA features (uveitis, psoriasis, enthesitis, dactylitis, good NSAID response, elevated CRP, family history). This patient meets “good NSAID response” + enthesitis + HLA‑B27 pending.
MRI STIR sequence: bone marrow edema adjacent to sacroiliac joints (active sacroiliitis) – hallmark of early axial spondyloarthritis even with normal X‑ray.
💡 Examiner probes: “Why do we order MRI despite normal X‑ray?” → Radiographic sacroiliitis takes years to develop; MRI detects active inflammation (osteitis/ bone marrow edema) allowing early diagnosis and treatment to prevent irreversible joint fusion.
🩸 Diagnostic approach – inflammatory markers, HLA-B27 & advanced imaging
1 Clinical assessment
Document inflammatory back pain (IBP) characteristics, enthesitis (Achilles, plantar fascia), dactylitis, uveitis history, psoriasis or IBD family history.
Document inflammatory back pain (IBP) characteristics, enthesitis (Achilles, plantar fascia), dactylitis, uveitis history, psoriasis or IBD family history.
2 Laboratory
ESR, CRP (elevated in ~50-70%), HLA‑B27 genotyping (positive in 80-90% of juvenile ankylosing spondylitis). CBC, RF, ANA (usually negative).
ESR, CRP (elevated in ~50-70%), HLA‑B27 genotyping (positive in 80-90% of juvenile ankylosing spondylitis). CBC, RF, ANA (usually negative).
3 Imaging (MRI sacroiliac joints)
STIR and T1-weighted sequences: bone marrow edema, erosions, fat metaplasia. Essential for “non‑radiographic axial SpA”.
STIR and T1-weighted sequences: bone marrow edema, erosions, fat metaplasia. Essential for “non‑radiographic axial SpA”.
4 Additional tests
X‑ray lumbar spine + pelvis (to assess for chronic changes, syndesmophytes, squaring). Whole-body MRI if peripheral enthesitis/arthritis. Ophthalmology slit-lamp exam to rule out asymptomatic anterior uveitis.
X‑ray lumbar spine + pelvis (to assess for chronic changes, syndesmophytes, squaring). Whole-body MRI if peripheral enthesitis/arthritis. Ophthalmology slit-lamp exam to rule out asymptomatic anterior uveitis.
📊 Key concept – Pre-radiographic vs radiographic axial SpA:
• Non‑radiographic (nr‑axSpA): clinical symptoms + MRI sacroiliitis (or HLA‑B27 + ≥2 SpA features) but normal X‑ray.
• Radiographic (AS): definite sacroiliitis on X‑ray (grade ≥2 bilaterally or grade 3 unilaterally – modified New York criteria).
• Both require same treatment paradigm; early diagnosis prevents ankylosis.
• Non‑radiographic (nr‑axSpA): clinical symptoms + MRI sacroiliitis (or HLA‑B27 + ≥2 SpA features) but normal X‑ray.
• Radiographic (AS): definite sacroiliitis on X‑ray (grade ≥2 bilaterally or grade 3 unilaterally – modified New York criteria).
• Both require same treatment paradigm; early diagnosis prevents ankylosis.
🧠 Differential diagnosis (examiner asks): mechanical low back pain, discitis/osteomyelitis, spondylolysis/spondylolisthesis, diffuse idiopathic skeletal hyperostosis (DISH), chronic recurrent multifocal osteomyelitis (CRMO), or referred pain from hip/sacroiliac joint. Normal RFT/UA rules out nephritis; normal X‑ray rules out spondylolysis.
🗨️ Examiner Q&A · Classification, Treatment & Prognosis (Chapter 197)
❓ Q1 (Examiner): “List the key features of inflammatory back pain (IBP) according to ASAS criteria.”
✅ Five ASAS features of IBP (at least 4/5 needed):
1. Age at onset <40 years.
2. Insidious onset.
3. Improvement with exercise.
4. No improvement with rest.
5. Pain at night (with improvement upon getting up).
➜ This patient has all except age <40 fulfilled.
1. Age at onset <40 years.
2. Insidious onset.
3. Improvement with exercise.
4. No improvement with rest.
5. Pain at night (with improvement upon getting up).
➜ This patient has all except age <40 fulfilled.
❓ Q2: “What is the role of HLA-B27 in juvenile spondyloarthritis? Is it diagnostic?”
✅ HLA‑B27 is not diagnostic but supports the diagnosis in the right clinical context (90% of JAS patients). It increases pretest probability. However, 7-10% of healthy population carry the allele. Negative HLA‑B27 does not exclude axial SpA, especially in females and non‑Caucasians.
❓ Q3: “This patient has normal X‑ray lumbosacral spine. Can we still diagnose axial spondyloarthritis?”
✅ Yes – “non‑radiographic axial SpA” (nr‑axSpA). According to ASAS criteria, if MRI shows active sacroiliitis (bone marrow edema/osteitis) plus at least one SpA feature (e.g., enthesitis, good NSAID response, arthritis, uveitis, dactylitis, positive family history, elevated CRP, HLA‑B27). Or if HLA‑B27 positive plus ≥2 SpA features, even without MRI changes.
❓ Q4: “Explain the treatment ladder for ERA/juvenile axial SpA (Nelson's Chapter 197).”
✅ Step 1: NSAIDs (naproxen, meloxicam, celecoxib) – continuous or on‑demand; good response supports diagnosis.
Step 2: physiotherapy (core strengthening, posture, stretching).
Step 3 (persistent active disease/axial): Biologic DMARDs: TNF inhibitors (etanercept, adalimumab, infliximab) – first-line for axial disease; also IL-17 inhibitors (secukinumab) approved for AS.
Note: Conventional DMARDs (sulfasalazine, methotrexate) work for peripheral arthritis but not for isolated axial symptoms.
Step 2: physiotherapy (core strengthening, posture, stretching).
Step 3 (persistent active disease/axial): Biologic DMARDs: TNF inhibitors (etanercept, adalimumab, infliximab) – first-line for axial disease; also IL-17 inhibitors (secukinumab) approved for AS.
Note: Conventional DMARDs (sulfasalazine, methotrexate) work for peripheral arthritis but not for isolated axial symptoms.
❓ Q5: “What extra‑articular manifestations are associated with juvenile spondyloarthritis?”
✅ • Acute anterior uveitis (pain, redness, photophobia) – 20-30% of HLA‑B27+ patients.
• Enthesitis (heel, patellar tendon, plantar fascia).
• Psoriasis or nail pitting (psoriatic arthritis overlap).
• Inflammatory bowel disease (subclinical gut inflammation seen on colonoscopy).
• Cardiac (aortic root dilation, conduction defects in long‑standing AS).
• Enthesitis (heel, patellar tendon, plantar fascia).
• Psoriasis or nail pitting (psoriatic arthritis overlap).
• Inflammatory bowel disease (subclinical gut inflammation seen on colonoscopy).
• Cardiac (aortic root dilation, conduction defects in long‑standing AS).
❓ Q6: “The patient’s mother asks about sports. What do you advise?”
✅ Encourage regular, low‑impact exercise – swimming, cycling, stretching, and physiotherapy. Avoid prolonged bed rest. Daily spinal mobility exercises reduce pain and maintain posture. Contact sports allowed as long as not triggering severe pain. Smoking cessation (if applicable) critical for preventing progression.
❓ Q7: “What is the prognosis of juvenile ankylosing spondylitis (JAS) compared to adult‑onset?”
✅ JAS often has more peripheral arthritis and enthesitis initially; axial symptoms may appear later. Hip involvement in childhood is a poor prognostic factor. With early anti‑TNF therapy, functional outcomes improve significantly. However, chronic course with flares is common; ~20% achieve remission within 5 years. Lifelong surveillance for uveitis, cardiovascular risk.
❓ Q8: “What baseline and monitoring tests are required before starting TNF inhibitor?”
✅ • Screening for latent tuberculosis (Quantiferon gold / PPD).
• Hepatitis B & C serology.
• Baseline CBC, LFTs, creatinine.
• Clinical assessment for demyelinating disease, heart failure.
• Vaccination update (influenza, pneumococcal, avoid live vaccines).
• Monitor every 3‑6 months: CBC, LFTs, TB risk questionnaire.
• Hepatitis B & C serology.
• Baseline CBC, LFTs, creatinine.
• Clinical assessment for demyelinating disease, heart failure.
• Vaccination update (influenza, pneumococcal, avoid live vaccines).
• Monitor every 3‑6 months: CBC, LFTs, TB risk questionnaire.
📘 Nelson's Chapter 197 – Management algorithm & key pearls
💊 First‑line: NSAIDs
Naproxen 15-20 mg/kg/day or meloxicam. Continuous use if needed; good response is diagnostic feature.
Naproxen 15-20 mg/kg/day or meloxicam. Continuous use if needed; good response is diagnostic feature.
🏃♂️ Physical therapy (essential)
Daily back extension exercises, respiratory training, postural correction, hydrotherapy.
Daily back extension exercises, respiratory training, postural correction, hydrotherapy.
🧬 Biologics (TNFi)
Adalimumab (FDA approved for ERA ≥2 years), etanercept, golimumab. Indicated for active sacroiliitis/axial disease refractory to NSAIDs.
Adalimumab (FDA approved for ERA ≥2 years), etanercept, golimumab. Indicated for active sacroiliitis/axial disease refractory to NSAIDs.
👁️ Ophthalmology screening
Slit‑lamp exam at diagnosis then every 6-12 months; treat asymptomatic uveitis early.
Slit‑lamp exam at diagnosis then every 6-12 months; treat asymptomatic uveitis early.
🩺 Monitoring
BASDAI score, morning stiffness duration, spinal mobility (Schober test, chest expansion), inflammatory markers.
BASDAI score, morning stiffness duration, spinal mobility (Schober test, chest expansion), inflammatory markers.
🚫 Avoid
Prolonged high‑dose steroids (no role for axial disease), smoking (worsens progression), delayed diagnosis.
Prolonged high‑dose steroids (no role for axial disease), smoking (worsens progression), delayed diagnosis.
📖 Direct quotation – Nelson's Chapter 197 (Ankylosing Spondylitis and other Spondyloarthritides):
“In children with enthesitis-related arthritis, inflammatory back pain may be underrecognized; MRI of the sacroiliac joints is the gold standard for early diagnosis of sacroiliitis. TNF‑α inhibitors have been efficacious in reducing symptoms and improving function. Physical therapy and low‑impact exercise should be included in all treatment programs.”
“In children with enthesitis-related arthritis, inflammatory back pain may be underrecognized; MRI of the sacroiliac joints is the gold standard for early diagnosis of sacroiliitis. TNF‑α inhibitors have been efficacious in reducing symptoms and improving function. Physical therapy and low‑impact exercise should be included in all treatment programs.”
⭐ TOACS TAKE‑HOME POINTS (Candidate must articulate):
1. Inflammatory back pain + morning stiffness + excellent NSAID response → suspect axial spondyloarthritis even if X‑ray normal.
2. MRI sacroiliac joints is crucial to detect active sacroiliitis (bone marrow edema) – do not rely on plain radiographs.
3. HLA‑B27 is supportive, not diagnostic; negative does not rule out disease.
4. First‑line treatment: NSAIDs + intensive physiotherapy. TNF inhibitors for persistent active disease.
5. Screen for uveitis, IBD, psoriasis. Monitor growth, spinal mobility, and psychological wellbeing.
6. Prognosis improves with early diagnosis and biologic therapy; prevent irreversible fusion.
1. Inflammatory back pain + morning stiffness + excellent NSAID response → suspect axial spondyloarthritis even if X‑ray normal.
2. MRI sacroiliac joints is crucial to detect active sacroiliitis (bone marrow edema) – do not rely on plain radiographs.
3. HLA‑B27 is supportive, not diagnostic; negative does not rule out disease.
4. First‑line treatment: NSAIDs + intensive physiotherapy. TNF inhibitors for persistent active disease.
5. Screen for uveitis, IBD, psoriasis. Monitor growth, spinal mobility, and psychological wellbeing.
6. Prognosis improves with early diagnosis and biologic therapy; prevent irreversible fusion.
ASAS classification criteria for axial spondyloarthritis: imaging arm (MRI sacroiliitis + 1 SpA feature) or clinical arm (HLA‑B27 + ≥2 SpA features). Essential for non‑radiographic disease.
🔗 Online resources for FCPS candidates:
• Paeds Online – TOACS banks & spondyloarthritis summary
• American College of Rheumatology – Juvenile Spondyloarthritis guidelines
• PRINTO – ERA diagnostic criteria
• Paeds Online – TOACS banks & spondyloarthritis summary
• American College of Rheumatology – Juvenile Spondyloarthritis guidelines
• PRINTO – ERA diagnostic criteria