What is the management approach for a 6-year-old with polyarthritis and fever?

Management of Polyarthritis with Fever in a 6-Year-Old

Initiate methotrexate as first-line DMARD therapy immediately after confirming the diagnosis of juvenile idiopathic arthritis (JIA), using subcutaneous administration at 10-15 mg/m²/week, combined with NSAIDs for symptom control, while avoiding chronic oral glucocorticoids entirely. 1, 2

Immediate Diagnostic Priorities

Before initiating treatment, you must:

• Exclude acute lymphoblastic leukemia (ALL) through complete blood count with differential and peripheral smear, as ALL presents with fever, polyarthritis, and bone pain in one-third of cases and can mimic systemic JIA 3
• Perform bone marrow examination if any suspicion exists before starting any glucocorticoid therapy, as steroids can mask leukemia 3
• Document arthritis duration ≥6 weeks to meet JIA diagnostic criteria, though treatment planning can begin earlier 2
• Count affected joints in first 6 months to classify as polyarticular JIA (≥5 joints) versus other subtypes 2
• Assess for systemic features including daily fever spikes, evanescent rash, lymphadenopathy, hepatosplenomegaly, and serositis to distinguish systemic JIA from polyarticular JIA 1, 4

Initial Treatment Algorithm

For Polyarticular JIA (Non-Systemic)

Start methotrexate immediately rather than NSAIDs alone, as DMARD monotherapy is strongly recommended over NSAID monotherapy for polyarticular disease 1, 5

Specific methotrexate dosing:

• Use subcutaneous route (conditionally recommended over oral due to superior bioavailability) 1
• Dose: 10-15 mg/m²/week based on pediatric trial data showing efficacy at 10 mg/m²/week 6
• Peak effect occurs at 3-6 weeks, with adequate trial duration being 3 months before considering escalation 1, 5

Add NSAIDs as adjunctive therapy for symptom control (conditionally recommended) 1

Consider bridging oral glucocorticoids (<3 months) only if moderate/high disease activity (cJADAS-10 >2.5), but this is conditional 1

Use intraarticular triamcinolone hexacetonide (strongly preferred over triamcinolone acetonide) for accessible symptomatic joints 1, 2

For Systemic JIA

If fever pattern is quotidian (daily spikes) with systemic features:

• Start NSAIDs as initial monotherapy (conditionally recommended) 5
• Strongly avoid conventional DMARDs (including methotrexate) as initial monotherapy 5
• Escalate to IL-1 or IL-6 inhibitors (anakinra, canakinumab, or tocilizumab) if inadequate response to NSAIDs, as these are strongly recommended over conventional DMARDs 5

Critical Treatment Principles

Never use chronic low-dose oral glucocorticoids regardless of disease activity or risk factors (strong recommendation), as they cause growth suppression and osteoporosis without preventing joint damage 1, 2

Escalate therapy aggressively to achieve low disease activity (cJADAS-10 ≤2.5) or inactive disease, as early aggressive treatment prevents permanent joint damage 1, 2

Add biologic DMARD to methotrexate (rather than switching to second conventional DMARD) if inadequate response after 3 months, with options including etanercept, adalimumab, abatacept, or tocilizumab 1, 5

Disease Activity Monitoring

Use validated cJADAS-10 score to guide treat-to-target approach:

• Target: cJADAS-10 ≤2.5 (low disease activity) or inactive disease 2, 5
• Moderate/high disease activity: cJADAS-10 >2.5 requires escalation 1
• Reassess at 6-8 weeks after initiating therapy; if minimal/no response, escalate immediately rather than waiting full 3 months 5

Essential Adjunctive Therapies

Initiate physical and occupational therapy from diagnosis for all patients with or at risk of functional limitations (conditionally recommended with low-quality evidence for PT, very low for OT) 1, 2

Common Pitfalls to Avoid

Do not delay DMARD initiation in polyarticular disease while attempting NSAID monotherapy, as this allows irreversible joint damage 2, 5

Do not confuse systemic JIA with polyarticular JIA, as treatment algorithms differ fundamentally—systemic JIA requires IL-1/IL-6 inhibitors rather than methotrexate as first-line therapy 5

Do not start glucocorticoids before excluding malignancy, particularly ALL, which can present identically to systemic JIA 3

Do not use leflunomide or sulfasalazine as first-line DMARDs, as methotrexate is conditionally recommended over these alternatives 1