Types of Juvenile Arthritis (JA)
There are several different types of juvenile arthritis. According to the CDC, three clinical classification schemes exist: juvenile rheumatoid arthritis (JRA), juvenile chronic arthritis (JCA), and juvenile idiopathic arthritis (JIA). The most common form of juvenile arthritis in the is JRA, which involves at least six weeks of persistent arthritis in a child younger than 16 years with no other type of childhood arthritis.
JRA can affect one joint or many and in some cases, it affects the entire body causing swollen lymph nodes, rashes, and fever. Commonly, the signs and symptoms of juvenile rheumatoid arthritis include:
Pain. Sometimes children do not complain of joint pain, yet they will limp — especially first thing in the morning or after a nap.
Swelling. Joint swelling is usually first noticed in larger joints like the knee.
Stiffness. Children with JRA often appear clumsier than usual, particularly in the morning or after naps.
JRA has three distinct subtypes: systemic (10 percent), polyarticular (40 percent), and pauciarticular (50 percent). For the latter two types, girls are much more commonly affected. For the systemic type, the peak age of onset is one to six years old, and about 50 percent of cases result in a very short stature in adulthood. In all types of JRA, about 40 to 45 percent of patients still have active disease after 10 years.
Researchers and doctors have great difficulty in describing the epidemiology of juvenile arthritis. No known cause has been pinpointed for most forms of JA, nor is there evidence to suggest that toxins, foods, or allergies cause children to develop the disease. Some research points toward a genetic predisposition, which means the combination of genes a child receives from family members may cause the onset of arthritis when triggered by other factors.
It is known that JA is usually an autoimmune disorder, in that the immune system attacks some of the body’s healthy cells and tissues. Scientists don’t know why this happens but some think it’s a two-step process in children: a child is genetically predisposed to get the condition and then something like a virus sets off the arthritis.