Juvenile idiopathic arthritis (JIA)

Information

Juvenile idiopathic arthritis (JIA) is arthritis of unknown aetiology that begins before the 16th birthday and persists for at least 6 weeks; other known conditions are excluded.  Key clinical features include:

• Early morning joint stiffness (EMS)

• Synovitis (seen as joint swelling)
• Enthesitis (inflammation at entheses)
• Loss of range of joint movement, often with pain at end of range
• Arthralgia

• Joint Deformity
• Associated with uveitis which can be asymptomatic – we will refer to Ophthalmology once diagnosed

Pain is not a common presenting feature of JIA. 

The chief differentials for a swollen joint are infection (septic arthritis or osteomyelitis), malignancy (particularly leukaemia or bone tumours) and trauma.

Blood tests looking for JIA are often normal and are therefore only helpful in excluding other causes of joint pain/swelling rather than JIA itself.  It is for this reason that in a well child with suspected JIA, who is being referred to Rheumatology, we would advise not doing any investigations at the point of referral.

BSR guidance states that healthcare practitioners should refer all children and young people with suspected JIA to the paediatric rheumatology team within 6 weeks of the onset of symptoms

There are several different sub types of JIA (see table below) with oligoarticular JIA being the most common. 

Oligoarthritis	Affects four or fewer joints, typically the large ones (knees, ankles, elbows). Most common subtype of JIA.
Polyarthritis	Affects five or more joints, often on both sides of the body (both knees, both wrists, etc.). May affect large and small joints
Systemic	Affects the entire body (joints, skin and internal organs). Symptoms may include a high spiking fever (103°F or higher) that lasts at least two weeks and intermittent rash
Psoriatic arthritis (PsA)	Joint symptoms and a scaly rash behind the ears and/or on the eyelids, elbows, knees, belly button and scalp.
Enthesitis-related	Also known as spondyloarthritis. Affects where the muscles, ligaments or tendons attach to the bone (entheses)
Undifferentiated	Symptoms don’t match up perfectly with any of the subtypes, but inflammation is present in one or more joints

Systemic onset JIA (SOJIA) is a serious medical condition that can be life-threatening and is associated with macrophage activation syndrome (MAS) – urgent discussion with Paediatric Rheumatology is advised.  SOJIA can be difficult to identify early in the course (as arthritis may not be present initially). It may present in many different ways and a high index of suspicion is needed. The disease is present equally in males and females with no preferential age of onset.

Diagnosis of SOJIA

Requires presence of arthritis accompanied or preceded by daily-spiking fever plus one or more of the following:

• Evanescent non-fixed macular rash (pink rash that characteristically coincides with fever peaks)
• Hepatomegaly or splenomegaly
• Generalised lymphadenopathy
• Serositis

The arthritis is often symmetrical and polyarticular and can be absent at onset and develop during disease course.