Juvenile Arthritis

If you thought that arthritis was something that happened only to old people, you were probably shocked to discover that kids can get arthritis, too.  Sadly, they can.  Arthritis is not just for old people.

The type of arthritis that older people typically get is the most common form of arthritis; it is called osteoarthritis.  Children don’t usually have their joints wear out like old people and athletes.  When children get arthritis, either the arthritis is due to a known disease, or it is due to an immune system malfunction.

Rare reaction to an infection, or diseases such as myositis, Kawasaki disease, scleroderma, and lupus can cause inflammation and joint pain.  In this case, the cause of the arthritis is known.  Reactive Arthritis falls into this category.

Other times the cause is unknown.  The medical term is idiopathic.  That’s what we see in Juvenile Idiopathic Arthritis.  For some unknown reason, the immune system attacks the joints (and organs) instead of defending against disease.  When the immune system attacks self, the disease is an autoimmune disease.

JIA

There are different types of Juvenile Idiopathic Arthritis.  The common features are:
  • disease onset before age 16, and
  • joint pain not caused by a known infectious-, inflammatory-, or haemato-oncologic disease.

Doctors distinguish between different types of JIA based on symptoms during the first six months of the disease.

Systemic-Onset JIA Previously called Stills Disease, in addition to joint pain, SoJIA (sometimes written sJIA) is noted for high spiking fevers and a salmon-colored rash.  Typically occurring in early childhood, 10-20% of JIA diagnoses are for SoJIA.  The prognosis is very good.

Oligoarticular JIA Previously called pauciarticular JRA, this type of JIA involves fewer than five joints during the first six months of disease.  Half of all JIA diagnoses are for 1-3 year old children (usually girls) with oligoarticular JIA.

    • Persistent Oligoarticular JIA is the diagnosis if, after six months, the number of joints affected remains less than five.
    • Extended Oligoarticular JIA is the diagnosis if joint involvement increases to five or more after the intitial six-months of disease.

Polyarticular JIA This form of JIA is subdivided into two groups depending on whether or not lab tests are positive for rheumatoid factor.

    • RF+ is sometimes called sero-positive.  It is considered the juvenile version of adult RA.  Affecting adolescent girls, less than five percent of JIA diagnoses are for this form of the disease.
    • RF- is sometimes called seronegative.  This type of polyarthritis is most frequently diagnosed in early childhood, and accounts for 15-20% of all JIA cases.

Enthesitis Related Arthritis (ERA-JIA) Enthesitis is part of the spondyloarthropathy family, a family of autoimmune diseases that are more likely to affect the spine than other types of JIA.  It is the only type of JIA to be more commonly diagnosed in boys than girls.  ERA constitutes only 1-7% of JIA diagnoses.

Psoriatic JIA Diagnosis of PsJIA can be challenging because it is possible for a child to have Psoriatic Arthritis without having any skin symptoms of psoriasis.  PsJIA is also considered a type of spondyloarthropathy.  With onset in mid-childhood, 2-15% of JIA cases are PsJIA.

Undifferentiated JIA Sometimes children definitely have a type of inflammatory arthritis, but do not meet the diagnostic criteria of one of the other forms of JIA.  Other times children appear to meet the diagnostic criteria of more than one type of JIA.  In these cases, doctors say that the disease hasn’t declared (differentiated) itself yet, and the diagnosis is Undifferentiated JIA.

People who receive a diagnosis of one of the forms of JIA do not receive a different diagnosis when they become adults.  The diagnosis remains JIA, even if the person lives to be 80 years old.

JRA

The term Juvenile Rheumatoid Arthritis is seen in older literature from the United States.  It included some, but not all, of the diseases now labeled JIA.  Rheumatologists now prefer to use the International League of Associations for Rheumatology’s JIA classification system.

JCA

The term Juvenile Chronic Arthritis is seen in older literature from Europe. Rheumatologists now prefer to use the International League of Associations for Rheumatology’s JIA classification system.

Sources:

ILAR Classification for JIA
Arthritis in Children
JIA for the Primary Care Practitioner
Early Identification of Juvenile Idiopathic Arthritis
Types of JIA
JIA: Epidemiology and Immunopathogenesis
Juvenile Arthritis in the Classroom
Juvenile Arthritis
Classification of Juvenile Arthritis
Growing Pains: The ILAR Classification of Juvenile Idiopathic Arthritis
Juvenile Idiopathic Arthritis – Orphanet
Juvenile Idiopathic Arthritis - printo.it
Juvenile Idiopathic Arthritis – Oxford University Hospital
Q&A About Juvenile Arthritis
Juvenile Spondyloarthropathies
Classification of juvenile spondyloarthritis: enthesitis-related arthritis and beyond
Juvenile Enthesitis-Related Arthritis
Enthesitis Related Arthritis – MedScape
Enthesitis Related Arthritis – OrphaNet
Outcome in patients with enthesitis related arthritis