Juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA), also known as juvenile rheumatoid arthritis (JRA), is the most common chronic arthritic disease of childhood and corresponds to a group of different subtypes.

Epidemiology

The estimated incidence is ~13 per 100,000 per annum ³. By definition, symptoms must start before 16 years of age. Females are more affected with F:M = 2:1.

Clinical presentation

Oligoarticular or polyarticular arthritis of a duration of 6 weeks or longer must be present to diagnose juvenile idiopathic arthritis.

Patients may present with an acute onset of symptoms or a more gradual onset. Symptoms are often worse in the morning but typically persist to some extent throughout the day.

In patients with systemic-onset (also known as Still disease), intermittent spiking fevers are typically noted, which helps distinguish juvenile idiopathic arthritis from other diseases such as infection, other inflammatory diseases and malignancy. Migratory salmon-colored light pink rash involving the trunk and/or extremities and hepatosplenomegaly are also frequently observed in patients with systemic-onset.

Pathology

There are several subtypes of juvenile idiopathic arthritis ^7,8:

• oligoarticular JIA

  • affects ≤4 joints in the first 6 months of illness

  • peak age: 1-6 years

  • mainly affects medium and large joints

• polyarticular JIA (pJIA)

  • affects ≥5 joints

  • peak age: 1-4 years; 7-10 years

  • mainly affects small and medium joints

• systemic onset JIA (Still disease, not to be confused with adult onset Still disease)

  • see above

  • arthritis may present weeks to months after the onset of systemic symptoms

Markers

A proportion of patients have serum rheumatoid factor ⁹.

Radiographic features

Imaging shows a varied spectrum of involvement, based on the severity and duration of the disease. There is usually a predilection for large joints rather than small joints.

Plain radiograph

The following may be seen:

• joints:

  • soft tissue swelling

  • osteopenia

  • loss of joint space

  • erosions

  • growth disturbances (epiphyseal overgrowth or "ballooning")

  • joint subluxation

• hips:

  • involved in ~35-63% of cases ¹⁵ (especially with enthesitis-related arthritis and polyarticular subtypes ¹⁴)

• knees: 

  • a widened intercondylar notch is associated (but can also be seen in hemophilic arthropathy and tuberculous arthropathy)

• cervical spine:

  • atlantoaxial subluxation

  • odontoid erosions

  • ankylosis, especially of the facet joints

• chest:

  • pericardial effusion

  • pleural effusion

• abdomen:

  • hepatosplenomegaly

MRI

MRI may show synovial hypertrophy, joint effusions and rice bodies ¹⁰, as well as osseous and cartilaginous erosions. Active synovitis is characterized by enhancement in T1-weighted gadolinium contrast studies.

Treatment and prognosis

Management includes physical therapy, weight control, nutrition counseling, and drugs. The most commonly used drug is methotrexate. Nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids and biologic response modifiers also may be used. Surgery is only used in advanced disease to improve joint function.