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| ==Background==
| | #REDIRECT [[Systemic Juvenile Idiopathic Arthritis (sJIA)]] |
| *Systemic juvenile idiopathic arthritis (sJIA) is also known as '''Still's disease''' (the adult form is adult-onset Still's disease)
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| *An '''autoinflammatory''' disease (driven by innate immune system and IL-1/IL-6), distinct from other forms of JIA which are autoimmune<ref name="StatPearls">Juvenile Idiopathic Arthritis. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024.</ref>
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| *Children <16 years; accounts for 10-20% of all JIA but contributes approximately two-thirds of JIA-related mortality<ref name="Behrens2008">Behrens EM, Beukelman T, Paessler M, Cron RQ. Occult macrophage activation syndrome in patients with systemic juvenile idiopathic arthritis. J Rheumatol. 2007;34(5):1133-8.</ref>
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| *Peak onset age 1-5 years; equal sex distribution (unlike other JIA subtypes)
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| *Most important differential diagnosis in a child presenting with prolonged [[fever of unknown origin]]
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| *sJIA is a diagnosis of exclusion — '''must rule out infection and malignancy first'''
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| ===ILAR Classification Criteria===
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| Arthritis in ≥1 joint with, or preceded by, fever of ≥2 weeks duration that is documented to be '''quotidian''' (daily) for ≥3 days, '''PLUS''' ≥1 of the following:<ref name="ILAR">Petty RE, Southwood TR, Manners P, et al. International League of Associations for Rheumatology classification of juvenile idiopathic arthritis: second revision, Edmonton, 2001. J Rheumatol. 2004;31(2):390-2.</ref>
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| #Evanescent (nonfixed) erythematous rash | |
| #Generalized [[lymphadenopathy]]
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| #[[Hepatomegaly]] and/or [[splenomegaly]]
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| #Serositis ([[pericarditis]], [[pleuritis]], or peritonitis)
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| ''Exclusions: Psoriasis in patient or first-degree relative, arthritis in HLA-B27+ male with onset after age 6, [[ankylosing spondylitis]]/ERA/sacroiliitis with IBD/reactive arthritis/acute anterior uveitis in first-degree relative, positive IgM RF on ≥2 occasions ≥3 months apart''
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| ==Clinical Features==
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| ===Fever===
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| *'''Quotidian''' (daily spiking) pattern: temperature spikes to ≥39°C (102.2°F), typically 1-2 times daily (often late afternoon/evening), with return to '''normal or below normal''' baseline between spikes<ref name="Raj2024">Spoorthy Raj DR, Suma Balan. Systemic Juvenile Idiopathic Arthritis: The Challenges and Opportunities. Indian J Rheumatol. 2024.</ref>
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| *Child may appear '''profoundly ill''' during fever spikes and '''remarkably well''' between them — this pattern is highly suggestive
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| *The classic quotidian pattern is observed in only ~37% of patients; atypical fever patterns are common<ref name="Raj2024"/>
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| *Duration ≥2 weeks by definition
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| *'''ED Pearl:''' Evolution from intermittent spiking fever to '''continuous high fever''' should raise concern for [[macrophage activation syndrome]] (MAS)
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| ===Rash===
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| *'''Evanescent''' (comes and goes), salmon-pink, macular or maculopapular
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| *Appears during fever spikes, resolves with defervescence — '''may be absent when the child is afebrile in the ED'''
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| *Trunk, proximal extremities, axillae, neck; spares face
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| *Non-pruritic, non-fixed, leaves no residual scarring or pigmentation
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| *'''Koebner phenomenon:''' rash may appear at sites of skin scratching or pressure<ref name="Raj2024"/>
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| *May be difficult to appreciate in '''dark-skinned children''' — examine during active fever
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| ===Arthritis===
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| *May be oligoarticular or polyarticular; wrists, knees, and ankles most commonly affected
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| *Arthritis '''may be delayed''' — systemic features can precede joint involvement by weeks to months
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| *Cervical spine and temporomandibular joint involvement more common in sJIA than other JIA subtypes
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| ===Other Features===
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| *[[Hepatomegaly|Hepatosplenomegaly]]
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| *Generalized [[lymphadenopathy]]
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| *'''Serositis:''' [[pericardial effusion]] (most common serosal involvement), [[pleural effusion]], peritonitis
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| *[[Myalgia]], severe malaise, weight loss, irritability
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| *Growth retardation (chronic disease)
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| ===Macrophage Activation Syndrome (MAS)===
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| '''''The most life-threatening complication of sJIA. Occurs in ~10% overtly, up to 30% subclinically.'''''<ref name="Ravelli2012">Ravelli A, Minoia F, Davì S, et al. 2016 Classification Criteria for Macrophage Activation Syndrome Complicating Systemic Juvenile Idiopathic Arthritis. Arthritis Rheumatol. 2016;68(3):566-76.</ref>
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| *A form of secondary [[hemophagocytic lymphohistiocytosis]] (HLH) — massive cytokine storm
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| *'''Triggers:''' viral infections, medication changes, disease flares
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| *'''Clinical red flags for MAS:'''
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| **'''Change in fever pattern''' from intermittent to '''continuous'''
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| **Worsening despite treatment, or rapid deterioration
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| **New or worsening [[hepatomegaly]]
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| **Hemorrhagic manifestations (bruising, mucosal bleeding)
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| **Encephalopathy, [[altered mental status]]
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| **'''Paradoxical drop in ESR''' (due to fibrinogen consumption) while [[ferritin]] is markedly elevated
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| *'''Lab hallmarks of MAS:'''
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| **'''Hyperferritinemia''' (often >10,000 ng/mL; markedly disproportionate to other acute phase reactants)
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| **↓ Fibrinogen (consumption)
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| **↓ Platelets (falling trend, even if still "normal")
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| **↓ WBC (falling trend)
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| **↑ AST/ALT (liver involvement)
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| **↑ Triglycerides
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| **↑ LDH
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| **↑ D-dimer / ↓ ESR (paradoxical — ESR drops as fibrinogen is consumed)
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| *'''ED Pearl:''' A falling platelet count, falling ESR, or rising ferritin in a child with sJIA should be considered MAS until proven otherwise and warrants emergent rheumatology and/or hematology consultation
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| ==Differential Diagnosis==
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| ''sJIA is a diagnosis of exclusion. The following must be considered before attributing findings to sJIA:''
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| ===Critical to Exclude===
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| *'''[[Leukemia]]/[[lymphoma]]''' — most important mimicker; can present with fever, arthralgia, hepatosplenomegaly, lymphadenopathy, and cytopenias
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| *'''[[Sepsis (Main)|Sepsis]]/bacteremia''' — especially [[endocarditis]]
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| *'''[[Kawasaki disease]]''' — prolonged fever, rash, lymphadenopathy (but typically <5 days fever at presentation, and specific mucocutaneous criteria)
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| *'''[[Neuroblastoma]]''' and other solid tumors
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| ===Other Differential===
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| *[[Acute rheumatic fever]]
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| *Viral infections ([[EBV]], [[CMV]], parvovirus B19, [[HIV]])
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| *[[Lyme disease]]
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| *Reactive arthritis
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| *[[Systemic lupus erythematosus]]
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| *[[Inflammatory bowel disease]] with extraintestinal manifestations
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| *PFAPA syndrome (periodic fever, aphthous stomatitis, pharyngitis, adenitis)
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| *Autoinflammatory syndromes (familial Mediterranean fever, TRAPS, etc.)
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| *[[Polyarteritis nodosa]]
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| *Castleman disease
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| {{Pediatric hip DDX}}
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| {{Differential Diagnosis Polyarthritis}}
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| ==Evaluation==
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| ===Workup===
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| *'''CBC with differential:'''
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| **Leukocytosis (often marked; WBC >15,000-50,000+; sometimes leukemoid reaction)
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| **Anemia (hypochromic, microcytic — anemia of chronic disease)
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| **Thrombocytosis (reactive) — '''a falling platelet count suggests MAS'''
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| *'''ESR, [[CRP]]:''' markedly elevated; '''paradoxical drop in ESR with rising CRP suggests MAS'''
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| *'''[[Ferritin]]:''' often very elevated in active sJIA (typically >500 ng/mL); '''ferritin >10,000 ng/mL strongly suggests MAS'''<ref name="Ravelli2012"/>
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| *'''Fibrinogen:''' normal or elevated in active sJIA; '''falling fibrinogen suggests MAS'''
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| *'''[[LFTs]]:''' may be elevated; transaminitis suggests MAS or hepatic involvement
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| *'''LDH, triglycerides, D-dimer:''' to screen for MAS
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| *'''[[Blood culture]]:''' mandatory to exclude bacteremia/sepsis
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| *'''Peripheral blood smear:''' to evaluate for blasts (leukemia) and hemophagocytes
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| *'''Coagulation studies''' (PT/PTT): may be prolonged in MAS/DIC
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| *Consider: [[procalcitonin]] (may help differentiate infection from sJIA flare, though not definitive), [[uric acid]], [[urinalysis]]
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| ===Imaging===
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| *'''[[CXR]]:''' evaluate for [[pleural effusion]], [[pericardial effusion]], or [[pneumonia]]
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| *'''[[Echocardiography]]:''' if concern for [[pericardial effusion]] or [[myocarditis]]
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| *'''Joint imaging:''' [[ultrasound]] or X-ray of affected joints to assess for effusion; may help distinguish from [[septic arthritis]]
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| ===Diagnosis===
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| *Clinical diagnosis based on ILAR criteria (see Background) after '''exclusion of infection and malignancy'''
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| *'''[[Arthrocentesis]]''' may be needed to exclude [[septic arthritis]] — especially if monoarticular presentation
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| *'''Bone marrow biopsy''' may be required to exclude leukemia if clinical concern exists, particularly before starting corticosteroids (which can mask leukemia)
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| *ANA and RF are typically '''negative''' in sJIA (if positive, consider other diagnoses)
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| *No single diagnostic test is confirmatory — the diagnosis rests on the combination of clinical features and exclusion of mimickers
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| ==Management==
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| ''Management in the ED is focused on stabilization, diagnostic workup, and rheumatology consultation. Definitive treatment is guided by pediatric rheumatology.''
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| ===Acute ED Management===
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| *'''Hemodynamic stabilization''' if MAS or sepsis is suspected
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| *Empiric '''[[antibiotics]]''' until sepsis/bacterial infection can be excluded (these patients often appear septic)
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| *'''[[NSAIDs]]''' for fever, pain, and mild-moderate disease:
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| **[[Naproxen]] 10-15 mg/kg/day divided BID (most commonly used NSAID in sJIA)
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| **[[Ibuprofen]] 30-40 mg/kg/day divided TID-QID
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| *'''[[Corticosteroids]]''' may be initiated if:
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| **Diagnosis is certain (infection and malignancy excluded)
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| **Severe systemic illness, [[pericarditis]], or MAS
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| **Typically [[methylprednisolone]] IV pulse (30 mg/kg, max 1g) for severe disease or MAS, or [[prednisone]] 1-2 mg/kg/day PO for moderate disease
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| **'''Do not start steroids before obtaining a peripheral smear and ideally a bone marrow biopsy if leukemia has not been excluded'''<ref name="StatPearls"/>
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| *If MAS suspected: emergent rheumatology and/or hematology consultation; high-dose IV corticosteroids are first-line; may require [[cyclosporine]] or anakinra
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| ===Definitive Therapy (Rheumatology-Directed)===
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| *'''IL-1 inhibitors''' ([[anakinra]], canakinumab) and '''IL-6 inhibitors''' ([[tocilizumab]]) are first-line biologic agents for moderate-severe sJIA<ref name="Ringold2023">Ringold S, Angeles-Han ST, Engel ME, et al. 2019 American College of Rheumatology/Arthritis Foundation Guideline for the Treatment of Juvenile Idiopathic Arthritis: Therapeutic Approaches for Systemic Juvenile Idiopathic Arthritis. Arthritis Care Res. 2022;74(4):521-533.</ref>
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| *Goal is early aggressive therapy to achieve remission and minimize corticosteroid exposure
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| *'''Anakinra''' (IL-1 receptor antagonist) may be started in the ED or inpatient setting by rheumatology for severe/refractory disease or MAS
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| ===Consults===
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| *'''Pediatric rheumatology:''' All patients with suspected sJIA
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| *'''Pediatric hematology/oncology:''' If leukemia/malignancy is on the differential, or if MAS is suspected
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| *'''Cardiology:''' If significant [[pericardial effusion]] or concern for [[cardiac tamponade]]
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| ==Disposition==
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| *'''Admit''' — nearly all patients with suspected new-onset sJIA require admission for:
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| **Diagnostic workup to exclude infection and malignancy
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| **Monitoring for MAS (which can develop at any point)
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| **Initiation of treatment
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| **Rheumatology consultation
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| *'''ICU admission''' if:
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| **MAS with hemodynamic instability, coagulopathy, or organ dysfunction
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| **Significant [[pericardial effusion]] with hemodynamic compromise
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| **Respiratory distress from [[pleural effusion]] or pulmonary disease
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| ==See Also==
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| *[[Hip Pain (Peds)]]
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| *[[Kawasaki disease]]
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| *[[Septic arthritis]]
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| *[[Leukemia]]
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| *[[Pericardial effusion and tamponade]]
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| *[[Acute rheumatic fever]]
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| *[[Fever of unknown origin]]
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| ==External Links==
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| *[https://www.arthritis.org/diseases/systemic-juvenile-idiopathic-arthritis Arthritis Foundation - Systemic JIA Overview]
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| *[https://www.ncbi.nlm.nih.gov/books/NBK554605/ StatPearls - Juvenile Idiopathic Arthritis]
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| ==References==
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| {{reflist|2}}
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| [[Category:Rheumatology]]
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| [[Category:Pediatrics]]
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