Juvenile idiopathic arthritis (JIA) 
the most common rheumatic disease in children
Criteria for the Classification
Age at onset: <16 yr
Arthritis
swelling or effusion, or the presence of ≥2 of :
limitation of range of motion
tenderness or pain on motion,
increased heat) in ≥1 joint
Duration of disease: ≥6 wk
Onset type defined by type of articular involvement in the 1st 6 mo after onset
Polyarthritis: ≥5 inflamed joints
Oligoarthritis: ≤4 inflamed joints
Systemic-onset disease: arthritis with rash and a characteristic quotidian fever
Oligoarthritis
≤4 joints within the 1st 6 mo of disease
onset
affects the large joints of the lower extremities, such as the knees
and ankles
Those in whom disease never develops in >4 joints 
persistent oligoarticular JIA ,
evolution of disease in >4 joints
after 6 mo changes the classification to extended oligoarticular JIA
associated with a worse prognosis.
Isolated involvement of the hip is almost
never a presenting sign and suggests ERA or a nonrheumatic
cause.
Polyarthritis
inflammation of ≥5 joints in both upper and
lower extremities
Rheumatoid nodules on the extensor surfaces of the
elbows, spine, and over the tendon Achilles = a more severe course
almost exclusively occur in RF-positive
individuals
Micrognathia reflects chronic temporomandibular
joint disease
Cervical spine involvement
manifesting
as decreased neck extension
atlantoaxial subluxation and
neurologic sequelae.
Hip disease may be subtle, with findings of decreased or painful ROM on examination
Systemic JIA is characterized
Fever
as spiking temperatures to ≥39°C
daily or twice-daily basis for at least 2 wk,
rapid return to normal or subnormal temperatures
in the evening
Rash
faint,
erythematous, macular rash.
salmon-colored lesions
usually distributed over the trunk and
proximal extremities
nonpruritic and migratory with lesions lasting <1 hr.
Koebner phenomenon :
a cutaneous hypersensitivity Caused by superficial trauma.
hepatosplenomegaly, and
lymphadenopathy are present in >70% of affected children.
Arthritis
classically polyarticular, may be very destructive, and
can include hip, cervical spine, and temporomandibular joint involvement.
Diagnosis
JIA is a clinical diagnosis without any diagnostic laboratory tests
clinical exclusion of other diseases and many mimics is therefore
essential.
ANA and RF, are only supportive or prognostic, and their results may be normal in patients with JIA
ANA seropositivity is associated with
increased risk of chronic uveitis in JIA
RF, is a marker of more aggressive disease.
Characteristic radiographic changes in cervical spine, most frequently in the
neural arch joints at C2-C3 , may progress to atlantoaxial
subluxation.
MRI is more sensitive than radiography to detect early changes.
Differential Diagnosis
Systemic lupus erythematosus
Juvenile dermatomyositis
Henoch-Schönlein purpura
Psoriatic arthritis
Reactive arthritis
Infectious Illnesses
Bacterial arthritis
Acute rheumatic fever
Immunodeficiencies
Gout
Thyroid disease (hypothyroidism, hyperthyroidism)
Vitamin C deficiency (scurvy)
Hereditary connective tissue disease (Marfan syndrome
Trauma
Neuropathic Disorders
Neoplastic Disorders
Leukemia
Neuroblastoma
Lymphoma
Bone tumors (osteosarcoma, Ewing sarcoma)
Hematologic Disorders
Hemophilia
Hemoglobinopathies (including sickle cell disease)
Treatment
The goals of treatment are :
disease remission,
prevent or halt joint damage
foster normal growth and development.
All children with JIA need
individualized treatment plans, and management is tailored according to disease
subtype and severity, presence of poor prognostic indicators, and response to
medications.
antiinflammatory drugs (NSAIDs), with improvement in inflammation and pain
Those who have no or partial response after 4-6 wk of treatment
with NSAIDs, or who have functional limitations such as joint contracture or
leg-length discrepancy, benefit from injection of intraarticular corticosteroids.
diseasemodifying antirheumatic drugs (DMARDs), including methotrexate, and, if no
response, TNF inhibitors.