Definition
• Group of inflammatory
arthropathies affecting children <
16
years old
Best
diagnostic clue
○ 4 subtypes differ in
clinical presentation and prognosis
○ Any affected joint has
similar attributes
– Large effusions
– Osseous erosions
– Cartilage destruction
– Often bilateral but usually
not symmetric
– End-stage ankylosis
□ Carpus most frequent site of
fusion
□ If cervical spine involved,
fusion of bodies and posterior elements frequently occurs
– Osteoporosis
Location
○ Subsets differ in joints
most likely to be affected
– Oligoarticular (> 50% of
cases)
□ Generally only 2-4 joints
□ Knee most frequent, followed
by ankle and elbow
– Psoriatic
arthritis/enthesitis-related arthritis (10% of cases)
□ Sacroiliac joints, knee,
ankle, hip
– Polyarticular [RF(+) or
RF(-)] (30% of cases)
□ 5+ joints
□ Hands/feet; may involve all
joints as in adult RA
– Systemic (10% of cases)
□ Polyarticular, following
pattern of adult RA
○ Location in hand/wrist
different from adult RA
– Pericapitate erosions
predominate in carpus
– Metacarpophalangeal involvement
does not dominate interphalangeal involvement
Morphology
○ Growth abnormalities common
– Gracile long bones (narrow
diameter, thin cortex)
– Short stature, hypoplastic
iliac wings
□ Due to chronic illness, lack
of weight bearing
□ Early epiphyseal closure due
to hyperemia
– Hypoplastic cervical
vertebral bodies
□ Due to body fusion prior to
skeletal maturity
□ Morphology is normal, but
fused bodies are uniformly small relative to unfused bodies
– Micrognathia: Hypoplastic
angle of mandible with temporomandibular joint erosions
– Ballooned (enlarged)
epiphyses
□ Overgrowth of epiphysis due
to hyperemia from inflammatory synovitis
□ Results in prominent,
enlarged epiphyses relative to diaphyses
□ Clinically, knobby enlarged
joints
□ Especially prominent in
knee, ankle, elbow
– Enlarged notches
□ Due to pressure erosion from
pannus
□ Noted in intercondylar notch
of knee and trochlear notch in elbow
Radiographic
Findings
• Uniform osteopenia
• Earliest radiographic signs
○ Periostitis: Seen only at
earliest stages, in young child
○ Differential growth of
epiphysis; often need contralateral side for comparison
• Purely erosive disease
• Uniform cartilage narrowing
• Large effusions
• Progressive destruction,
with ankylosis at end-stage
• Growth abnormalities
○ Short stature
○ Gracile long bones
○ Overgrown epiphyses with
enlarged notches
MR
Findings
• MR provides information at
early stage, prior to radiographic change
○ Effusions, tenosynovitis:
High T2WI
○ Marrow edema: Low T1WI, high
T2WI signal
○ Erosions: Low T1WI, high
T2WI signal
○ Pannus: Thickened synovium
– Low signal on T1WI
– Low signal on T2WI, may be
nodular, outlined by high signal effusion
– Enhances with contrast
administration
○ Menisci may appear small or
compressed due to effusion
○ Contrast essential to
distinguish active synovial inflammation from nonenhancing effusion or fibrotic
pannus
• May be used to evaluate for
early physeal fusion when evaluating for growth potential
Etiology
○ Cause unknown
– Disordered immunoregulation
reported
– Possible latent viral
infection (rubella suggested)
– Likely not common cause
among subsets
Genetics
○ Associated with IL2RA (CD25)
gene (IL-2 receptor α)
– General susceptibility gene
for autoimmune diseases; likely represents JIA susceptibility locus
○ JIA patients carrying TNF-α -308 GA/AA and
-238 GA genotypes → worse prognosis and lower response to anti-TNF-α drugs
Associated
abnormalities
○ Oligoarticular: Serious risk
of uveitis
– May be complicated by
blindness
○ Psoriatic
arthritis/enthesitis-related arthritis
– 50% HLA-B27(+)
○ Polyarticular:
Constitutional symptoms
– Low-grade fever, weight loss
– Lymphadenopathy
– Rheumatoid factor positive
in 20-30%
– ANA(+) in 40%
○ Systemic
– Quotidian (daily spiking) fever,
rash
– Lymphadenopathy
– Hepatosplenomegaly
– Weight loss, myalgia
– Neutrophilic leukocytosis,
anemia
– Rheumatoid factor and ANA
(-); ↑ ESR
TOP
DIFFERENTIAL DIAGNOSES
• Hemophilic arthropathy
• Toxic synovitis of hip
• Chronic septic joint
Lateral radiograph shows the unaffected knee in a
child with oligoarticular juvenile idiopathic arthritis (JIA). This is shown
for comparison.
Lateral radiograph shows the contralateral affected knee in the same patient. Although at 1st glance this radiograph appears normal, there is significant overgrowth of the epiphyses of this knee. Note the femoral condyles, proximal tibial epiphysis, and in particular the patella . There is also crenulation or irregularity along the femoral condyles .
AP radiograph shows the normal knee in the same child.
AP radiograph of the affected knee was taken at
the same distance and time. Note the enlargement of the femoral condylar and
proximal tibial epiphyses. This occurs due to the hyperemia of the joint
secondary to inflammation and synovitis. Such overgrowth, or ballooning, is
often the 1st radiographic sign of JIA. Note also the more mature morphology
of the medial tibial epiphysis .
Without comparison radiographs, it may easily be missed.
PA radiograph shows the hand in a child with new onset
of metacarpophalangeal pain and swelling (the right worse than the left). This
left hand appears normal.
PA radiograph of the right hand in the same
patient is shown. Compare the 3rd metacarpal head; it is enlarged and eroded. Additionally, there is relative overgrowth
of the base of the proximal phalanx . Note the soft tissue swelling. This focally
advanced skeletal maturation is secondary to hyperemia from the inflammatory
process.
Lateral radiograph in a young child shows regular
periosteal reaction extending along the phalanges . There is soft tissue swelling but no articular abnormality.
PA radiograph in the same child shows the same
subtle but regular periosteal reaction . The differential diagnoses for this appearance include JIA,
sickle cell dactylitis, and tuberculosis dactylitis. This proved to be an early
manifestation of JIA.
Lateral radiograph of the cervical spine in JIA
shows the typical ankylosis of posterior elements as well as vertebral bodies,
extending from C2-C6 . With fusion at a young
age, growth is arrested, leaving hypoplasia of the involved bodies compared with uninvolved ones .
Lateral radiograph in a JIA patient with C2-C6
fusion and hypoplasia over that
interval is shown. There is micrognathia, with hypoplastic angles of the mandible
and eroded temporomandibular joints .
AP radiograph of the knees in a patient with longstanding
JIA shows ballooned overgrowth of the femoral condyles and widening of the
intercondylar notch. Additionally, there is uniform cartilage thinning and prominent
subchondral erosions.
AP radiograph in the same patient shows
destruction of the hip joints with associated protrusio, typical of JIA.
PA radiograph of the carpus in a child with JIA shows
early fusion at several sites, including capitatemetacarpal , trapezoidmetacarpal , trapeziumtrapezoid , and hamatetriquetrum . The cortex appears
slightly irregular or crenulated. Carpal ankylosis is typical of JIA.
PA radiograph in a young adult who developed JIA
as a teenager shows near-complete carpal ankylosis .This is common in JIA but is not expected in adult rheumatoid arthritis.
AP radiograph in a child with JIA shows erosions along the lateral femoral neck . This portion of the hip is within the capsule and constitutes a bare area of bone, which is not protected by cartilage. It is at risk for early erosion. There is also cartilage narrowing .
AP radiograph in the same child, 1 year later,
shows the neck erosions have smoothed , leaving a thin neck at risk for fracture. There is complete
cartilage loss as well as subchondral erosions .
AP radiograph shows JIA, with widening of the trochlear
notch due to pressure erosion from pannus over a long period of time.
The radial head is relatively enlarged due to continual hyperemia in the joint. All growth centers may
enlarge, but in the elbow, the radial head shows disproportionate overgrowth.
Coronal STIR MR of the sacroiliac joints in an 8 year old shows bilateral asymmetric sacroiliitis , with erosions and cysts . This is the enthesitis-related arthritis subtype of JIA.
AP radiograph shows classic severe JIA in a
patient who is now an adult. There is overgrowth of the femoral condyles and a
widened intercondylar notch superimposed
on the erosive destructive inflammatory changes .
Lateral radiograph shows overgrowth of the femoral condyles and patella, developed secondary to chronic hyperemia prior to skeletal maturation. The widened intercondylar notch can be diagnosed on the lateral view by bowing of the Blumensaat line
AP radiograph shows the adult sequela of JIA,
with iliac wing hypoplasia and gracile femur which are the results of chronic illness and infrequent weight
bearing. There is protrusio of the hip, with severe destruction .
PA radiograph shows ulnar tilt due to overgrowth
of the radial styloid during the hyperemic
growing stage of JIA. Note the matching overgrowth of the ulnar styloid . The
collapsed radial aspect of the lunate likely resulted from erosions & impaction
from mild trauma.