One of the most common remarks I hear when I tell people what I do is “You’re a pediatric rheumatologist! I didn’t know children get arthritis!” But some children do.
Childhood arthritis is not common, and people, especially parents, do not expect a child to have joint complaints. Most children who complain of limping, joint swelling, or pain do so because they have had an injury or an infection, but there are a small proportion of children who develop arthritis. We call this Juvenile Idiopathic Arthritis (JIA).
Formerly known as JRA, the term has changed to reflect its difference from the rheumatoid arthritis that affects adults. JIA is not just one disease; it is a term that covers the spectrum of childhood arthritis. Childhood arthritis is categorized according to the pattern of joint involvement.
Pauciarticular (meaning few joints) JIA: This is the most common form of childhood arthritis. It affects no more than four joints, usually the large joints, in the first six months of illness. It occurs most commonly in girls with early onset, between one and four years of age.
Symptoms are sometimes mild and may go unrecognized in a child who is learning to walk. Any child who is limping, starts “walking funny,” or who has joints that cannot be moved completely due to pain or limitation should be assessed promptly. Pauciarticular arthritis is associated commonly with inflammatory eye disease, particularly if children are positive for an antibody in the blood called “antinuclear antibody.”
Early treatment of pauciarticular disease minimizes the risk of joint damage and limb length discrepancy, which occurs because a “hot,” swollen joint grows more quickly than a normal joint, and the affected leg may grow longer.
In its uncomplicated form, pauciarticular disease usually affects a single knee or ankle. Children are often ANA positive, but otherwise have only mild changes in their blood work. They respond rapidly to therapy. While there are some children with more complicated disease that may require more aggressive therapy and / or may have greater frequency of disease flare ups, the prognosis for children with uncomplicated JIA is good. A majority of patients have complete resolution of their symptoms over time.
Polyarticular (meaning many joints) JIA: This form of arthritis involves more than four joints in the first six months of the disease onset. It usually begins in several joints, often including the hands and fingers.
This disease is variable. It occurs more commonly in girls at all ages. There are two peaks in age at onset: young children between 18 months and eight years, and teenagers whose disease often starts after the onset of puberty. A subset of these patients may be positive for a blood test called “rheumatoid factor” and can be considered to have early onset adult type rheumatoid arthritis.
The differential diagnosis for polyarticular JIA includes reactive or infection associated arthritis, as well as other autoimmune conditions, including systemic lupus erythematosus.
Patients with polyarticular JIA are unlikely to “grow out” of their disease, but the prognosis for functionality with treatment is very good.
Systemic onset JIA: This is a condition that is characterized by arthritis, fever, and a classic salmon pink colored rash. It is a very different condition from the other forms of childhood arthritis and probably would be better classified as an autoinflammatory condition.
Boys and girls are affected equally. Patients typically present looking extremely ill, with recurring high fevers and abnormal blood work: including markedly elevated inflammatory markers and a worsening anemia. The joint complaints may not be present initially, or may be overlooked. These children are often thought to have an infection and are treated with antibiotics before systemic onset disease is considered.
An important feature of systemic onset disease is its very typical fever pattern; the temperature returns to normal at least once each day. At this time, the children generally look much improved and the rash often retreats.
Systemic onset arthritis is named as such because multiple organ systems may be involved, including the heart, liver, spleen, kidneys, and bone marrow.
Spondyloarthropathy: This term means “arthritis of the back” and describes a pattern of arthritis that commonly involves the spine, sacroiliac joints, and inflammation of the tendons at their insertion around the joints (enthesitis). Many different conditions are associated with this pattern of disease, including reactive arthritis, ankylosing spondylitis, and the arthritis associated with inflammatory bowel disease.
The medications used to treat JIA range from nonsteroidal anti-inflammatory drugs to traditional disease modifying agents, such as methotrexate and cyclosporine, to the now commonly used newer biologic agents. Steroids are sometimes needed, but their use is kept to a minimum due to their broad side effect profile.
All children with JIA are at increased risk of an inflammatory eye disease called uveitis, which can cause silent damage to the eyes, even if joint complaints are under control. They should be seen by an ophthalmologist (an eye doctor with an M.D. after his or her name) at least twice yearly.
Ongoing research into childhood arthritis is making great strides towards understanding the disease and its control. New therapies are broadening our treatment options and improving outcomes.
At Hospital for Special Surgery, the Pediatric Rheumatology Department is happy to provide any child displaying symptoms of childhood arthritis with the advice and treatment they need.