Rheumatology · Pediatric Rheumatology
The facts most likely to be tested
Juvenile Idiopathic Arthritis is defined as arthritis lasting at least six weeks in a child younger than 16 years old with no other identifiable cause.
Oligoarticular JIA is the most common subtype, typically affecting four or fewer joints in the lower extremities of young girls.
Patients with oligoarticular JIA are at high risk for chronic anterior uveitis, necessitating routine slit-lamp examinations by an ophthalmologist.
Systemic JIA (Still disease) presents with the classic triad of quotidian fever, a salmon-colored evanescent rash, and hepatosplenomegaly or lymphadenopathy.
Polyarticular JIA involves five or more joints and is categorized as either rheumatoid factor (RF) positive or negative, with the former mimicking adult rheumatoid arthritis.
Antinuclear antibody (ANA) positivity is a strong predictor for the development of uveitis in patients with oligoarticular JIA.
First-line pharmacologic therapy for JIA involves nonsteroidal anti-inflammatory drugs (NSAIDs), followed by methotrexate for patients who fail initial therapy or have high-risk features.
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A 4-year-old girl is brought to the clinic by her mother due to a persistent limp and swelling of the right knee for the past 8 weeks. Physical examination reveals a warm, swollen right knee with decreased range of motion, but no systemic symptoms such as fever or rash. Laboratory studies show a positive antinuclear antibody (ANA) titer, while inflammatory markers are mildly elevated. The child has no history of trauma or recent infection.
What is the most appropriate next step in the management of this patient?
Referral for a slit-lamp eye examination
The patient meets the criteria for oligoarticular JIA, and her positive ANA status places her at high risk for asymptomatic chronic anterior uveitis, which can lead to permanent vision loss if not detected early.
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High yield triage
Etiology / Epidemiology
Chronic autoimmune arthritis in children <16 years old lasting >6 weeks. Most common rheumatic disease of childhood.
Clinical Manifestations
Morning stiffness, gelling phenomenon, and joint swelling. Oligoarticular is the most common subtype.
Diagnosis
Clinical diagnosis of exclusion. ANA is often positive in oligoarticular disease.
Treatment
NSAIDs are first-line. Do not use aspirin due to Reye syndrome risk.
Prognosis
Risk of uveitis requires regular slit-lamp exams. Most achieve remission with early intervention.
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Epidemiology & Etiology
JIA is a diagnosis of exclusion in patients <16 years old with persistent arthritis for >6 weeks. It is an autoimmune condition with unknown triggers, though genetic predisposition (HLA associations) plays a role. It is the most common chronic rheumatic disease in children.
Pertinent Anatomy
Affects synovial joints, most commonly the knees, ankles, and wrists. Involvement of the cervical spine can lead to restricted range of motion. The ciliary body and iris are the primary sites of extra-articular involvement in uveitis.
Pathophysiology
T-cell mediated autoimmune response leads to chronic synovial inflammation and hyperplasia. This results in the production of inflammatory cytokines like TNF-alpha and IL-6. Persistent inflammation causes cartilage destruction, bony erosions, and potential growth disturbances like leg-length discrepancy.
Clinical Manifestations
Patients present with joint pain, swelling, and the gelling phenomenon (stiffness after inactivity). Oligoarticular JIA (≤4 joints) is the most common form and carries a high risk of asymptomatic uveitis. Red flags include systemic symptoms like high-spiking fevers, salmon-colored rash, and hepatosplenomegaly, which suggest Still's disease.
Diagnosis
Diagnosis is clinical; there is no single gold standard test. Labs are used to rule out mimics: ESR and CRP are often elevated. ANA positivity is a strong predictor for the development of chronic anterior uveitis.
Treatment
NSAIDs (e.g., naproxen) are the initial therapy for symptom control. If ineffective, methotrexate is the preferred DMARD. Aspirin is contraindicated in children due to the risk of Reye syndrome. Biologics like TNF-inhibitors are reserved for refractory cases.
Prognosis
The most critical complication is chronic anterior uveitis, which is often asymptomatic and can lead to blindness. Patients require regular slit-lamp examinations by an ophthalmologist. Early diagnosis and aggressive treatment are essential to prevent permanent joint damage and growth retardation.
Differential Diagnosis
Septic arthritis: acute onset with high fever and monoarticular involvement
Leukemia: bone pain often out of proportion to joint findings with cytopenias
Reactive arthritis: follows GI or GU infection
Lyme arthritis: history of tick bite and erythema migrans
SLE: multisystem involvement with malar rash and positive anti-dsDNA