JIA - Differential Diagnosis And Management

Differential Diagnosis Classification

Juvenile idiopathic arthritis requires meticulous clinical exclusion of other diseases.

Table 1: Differential Diagnosis Of Childhood Arthritis

Disease Category	Specific Conditions
Infectious Diseases	Septic arthritis, viral arthritis (rubella, parvovirus B19, Epstein-Barr virus, hepatitis B), Lyme disease, osteomyelitis, endocarditis.
Reactive And Post-Infectious	Acute rheumatic fever, reactive arthritis (enteric or urogenital triggers), transient synovitis of the hip.
Rheumatic And Autoimmune	Systemic lupus erythematosus, juvenile dermatomyositis, scleroderma, IgA vasculitis, Kawasaki disease, sarcoidosis, mixed connective tissue disease.
Neoplastic Disorders	Leukemia, neuroblastoma, lymphoma, bone tumors.
Orthopedic And Mechanical	Trauma, growing pains, hypermobility syndromes, Legg-Calve-Perthes disease, slipped capital femoral epiphysis, chondrolysis.
Autoinflammatory Syndromes	Periodic fever syndromes, macrophage activation syndrome, familial Mediterranean fever.
Immunodeficiencies	Hypogammaglobulinemia, IgA deficiency, common variable immunodeficiency.
Congenital And Metabolic	Gout, mucopolysaccharidoses, thyroid disease, scurvy, skeletal dysplasias.

Differentiating Features

Acute rheumatic fever causes exquisitely painful, migratory polyarthritis.
Malignancy exhibits nocturnal bone pain awakening children from sleep.
Malignancy demonstrates disproportionate pain relative to physical findings.
Leukemia presents with leukopenia, low-normal platelets, and high erythrocyte sedimentation rate (ESR).
Bone marrow examination remains mandatory confirming malignant infiltration.
Transient synovitis causes acute hip pain following viral infections.
Septic arthritis presents as an acute, painful, erythematous, hot single joint.
Synovial fluid aspiration excludes septic arthritis definitively.

Management Principles

Treatment Goals

Achieve complete disease remission.
Prevent or halt joint damage and deformities.
Foster normal psychosocial and physical growth.

Pharmacological Interventions

Table 2: Pharmacotherapy Agents And Indications

Drug Class	Specific Agents	Pediatric Dosage	Clinical Indications And Notes
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)	Naproxen	10–20 mg/kg/day PO divided q12h (Max: 1000 mg/day)	Initial symptomatic therapy relieving pain and stiffness.
	Ibuprofen	30–40 mg/kg/day PO divided q6-8h (Max: 2400 mg/day)	Initial symptomatic therapy relieving pain and stiffness.
	Meloxicam	0.125 mg/kg PO once daily (Max: 7.5 mg/day)	Initial symptomatic therapy relieving pain and stiffness.
Glucocorticoids	Triamcinolone hexacetonide	1 mg/kg per large joint (knee/hip); 0.5 mg/kg per small joint (Max: 40 mg per joint)	Intra-articular injection preferred for oligoarthritis.
	Prednisolone	0.5–2 mg/kg/day PO (Max: 60 mg/day); use lowest effective dose for bridge	Systemic route serves as bridge therapy or controls severe systemic JIA.
Conventional Synthetic DMARDs	Methotrexate	10–15 mg/m²/week SC or PO once weekly (Max: 25 mg/week)	Anchors treatment for polyarthritis and extended oligoarthritis.
	Sulfasalazine	30–50 mg/kg/day PO divided q12h; start low and titrate upward (Max: 2000 mg/day)	Targets enthesitis-related arthritis.
	Leflunomide	Weight-based: <40 kg: 10 mg every other day or daily; >40 kg: 10–20 mg PO once daily	Alternate conventional DMARD option.
Biologic DMARDs (Anti-TNF)	Etanercept	0.8 mg/kg/week SC once weekly (Max: 50 mg/week)	Targets polyarthritis refractory to methotrexate.
	Adalimumab	Weight-based: 10 to <15 kg: 10 mg; 15 to <30 kg: 20 mg; ≥30 kg: 40 mg SC every 2 weeks	Preferred treating associated uveitis.
	Infliximab	6 mg/kg IV infusion at weeks 0, 2, 6, then every 8 weeks	Used off-label for refractory polyarticular JIA/uveitis.
	Golimumab	30 mg/m² SC every 4 weeks (Max: 50 mg per dose)	Treats polyarticular JIA.
Biologic DMARDs (Anti-IL-1)	Anakinra	1–2 mg/kg/day SC once daily (Max: 100 mg/day); up to 4 mg/kg/day in MAS	Highly effective treating systemic JIA.
	Canakinumab	Weight-based: ≤75 kg: 4 mg/kg SC every 4 weeks; >75 kg: 300 mg SC every 4 weeks	Highly effective treating systemic JIA.
Biologic DMARDs (Anti-IL-6)	Tocilizumab	sJIA: <30 kg: 12 mg/kg IV q2w; ≥30 kg: 8 mg/kg IV q2w pJIA: <30 kg: 10 mg/kg IV q4w; ≥30 kg: 8 mg/kg IV q4w	Manages systemic JIA and macrophage activation syndrome.
T-Cell Modulators	Abatacept	IV: <75 kg: 10 mg/kg q4w SC: 10 to <25 kg: 50 mg/week; 25 to <50 kg: 87.5 mg/week; ≥50 kg: 125 mg/week	Inhibits T-cell activation treating polyarticular JIA.
Small Molecules (JAK Inhibitors)	Tofacitinib	Oral Solution/Tablet: <40 kg: 5 mg (5 mL) PO q12h; ≥40 kg: 5 mg tablet PO q12h	Treats polyarticular JIA targeting intracellular signaling.

Subtype-Specific Approach

Oligoarthritis management utilizes NSAIDs or intra-articular corticosteroids initially.
Methotrexate addition indicated for extended oligoarthritis or refractory disease.
Polyarthritis demands early aggressive therapy utilizing methotrexate.
Biologic tumor necrosis factor (TNF) antagonists added upon methotrexate failure.
Systemic JIA therapy utilizes corticosteroids alongside interleukin-1 or interleukin-6 antagonists.
Enthesitis-related arthritis responds to NSAIDs, sulfasalazine, and TNF inhibitors.
Macrophage activation syndrome requires pulse intravenous methylprednisolone and cyclosporine.

Multidisciplinary Rehabilitation

Physical therapy prevents fixed flexion contractures and maintains joint mobility.
Occupational therapy provides customized splints facilitating activities of daily living.
Routine slit-lamp ophthalmologic screening mandatory detecting asymptomatic uveitis.
Nutritionist consultation addresses growth failure and osteopenia secondary to chronic inflammation.
Psychosocial support essential addressing depression, school absenteeism, and chronic pain impact.