Juvenile idiopathic arthritis

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Juvenile idiopathic arthritis (JIA), formerly known as juvenile rheumatoid arthritis (JRA), is the most common form of persistent arthritis in children.

JIA is sometimes referred to as juvenile chronic arthritis (JCA), a term that is not precise as JIA does not encompass all forms of chronic childhood arthritis.

Arthritis is the inflammation of the synovium (the lining tissues) of a joint. JIA is a subset of arthritis seen in childhood, which may be transient and self-limited or chronic. It differs significantly from arthritis commonly seen in adults (osteoarthritis, rheumatoid arthritis), and other types of arthritis that can present in childhood which are chronic conditions (e.g. psoriatic arthritis and ankylosing spondylitis).

Symptoms
Symptoms of JIA are often non-specific initially, and include lethargy, reduced physical activity, and poor appetite. The first manifestation, particularly in young children, may be limping. Children may also become quite ill, presenting with flu-like syptoms that persist. The cardinal clinical feature is persistent swelling of the affected joint(s), which commonly include the knee, ankle, wrist and small joints of the hands and feet. Swelling may be difficult to detect clinically, especially for joints such as those of the spine, sacroiliac joints, shoulder, hip and jaw, where imaging techniques such as ultrasound or MRI are very useful.

Pain is an important feature of JIA, but young children may have difficulty in communicating this symptom. Late effects of arthritis include joint contracture (stiff, bent joint) and joint damage. Children with JIA vary in the degree to which they are affected by particular symptoms.

Etiology
The cause of JIA, as the word idiopathic suggests, is unknown and currently an area of active research. Current understanding of JIA suggests that it arises in a genetically susceptible individual due to environmental factors.

Types of JIA
The 3 major types of JIA are oligoarticular JIA, polyarticular JIA and systemic JIA.

Oligoarticular (pauciarticular) JIA
Oligoarticular (or pauciarticular) JIA affects 4 or fewer joints. Oligo means few. It was previously known as pauciarticular JIA. Patients with oligoarticular JIA are more often ANA positive, when compared to other types of JIA.

Polyarticular JIA
Affecting 5 or more joints in the first 6 months of disease. This subtype can include the affect of the neck and jaw as well as the small joints usually affected. This type of JIA is more common in small girls to that of boys.

Systemic JIA (Still's Disease)
Is characterized by arthritis, fever and a salmon pink rash. Systemic JIA can be challenging to diagnose because the fever and rash come and go. It affects males and females equally, unlike the other two subtypes of JIA.

Systemic JIA may have internal organ involvement and lead to serositis (e.g. pericarditis).

Onset
JIA occurs in both sexes. Symptoms onset is frequently dependent on the subtype of JIA (see Types of JIA) and is from the pre-school years to the early teenage years.

Prevalence
Juvenile idiopathic arthritis affects an estimated 300,000 children in the United States. Of these children, 50 percent have pauciarticular JIA, 40 percent have polyarticular JIA and 10 percent have systemic JIA.

Extra-articular manifestations
1. Eye disease: JIA is associated with inflammation in the front of the eye (chronic anterior uveitis). This complication may not have any symptoms and can be detected by an experienced ophthalmologist using a slit lamp. Most children with JIA are enrolled in a regular slit lamp screening program, as poorly controlled chronic anterior uveitis may result in permanent eye damage, including blindness.

2. Growth disturbance: Children with JIA may have reduced overall rate of growth, especially if the disease involves many joints or other body systems. Paradoxically, individually affected large joints (such as the knee) may grow faster, due to inflammation - induced, increased blood supply to the bone growth plates situated near the joints

Treatment
The treatment of JIA is best undertaken by an experienced team of health professionals, including paediatric rheumatologists, nurse specialists, physiotherapists, occupational therapists, chiropractors and psychologists. Many others in the wider health and school communities also have valuable roles to play, such as ophthalmologists, dentists, orthopaedic surgeons, school nurses and teachers, careers advisors and, of course local general practitioners, paediatricians and rheumatologists. It is essential that every effort is made to involve the affected child and their family in disease education and balanced treatment decisions.

There have been very beneficial advances in drug treatment over the last 20 years. Most children are treated with non-steroidal anti-inflammatory drugs and intra-articular corticosteroid injections. Methotrexate is a powerful drug which helps suppress joint inflammation in the majority of JIA patients with polyarthritis and systemic arthritis. Newer drugs have been developed recently, such as TNF alpha blockers, which appear to be effective in severe JIA. There is little or no controlled evidence to support the use of alternative remedies such as specific dietary exclusions, homeopathic treatment or acupuncture.