Chronic Arthritis of Childhood
One of the most frequent chronic diseases of children and the most common rheumatological condition in this group is juvenile rheumatoid arthritis. This is not one disorder but a group of interrelated disorders which all exhibit inflammatory changes in the joints. The triggering factors for these diseases have not been uncovered and it has proven hard to delineate one particular type of condition from another due to the complex genetic factors. While it is often called JRA, there is a move to standardise the naming of these diseases into juvenile idiopathic arthritis.
Three main divisions of juvenile rheumatoid arthritis can be described, that affecting many joints which is called polyarticular, that involving few joints and termed pauciarticular and a more body wide disease onset known as systemic arthritis. The arthritis is a chronic disease which flares up at times and then goes into remissions, with targeting of the medical treatment towards the induction and maintenance of a remission. Recent advances in the development of drugs have produced the biological agents which are much more effective for arthritic diseases.
The triggering factors for juvenile rheumatoid arthritis have not been clearly identified, with a possible trigger of trauma or infection developing an autoimmune attack against joint tissues. The synovial lining of the joint increases in bulk and develops chronic inflammation, with perhaps some genetic vulnerability contributing to this process. A group of genes are understood to be involved in the pattern of disease presentation and the nature of its onset. There are many factors which influence the incidence of these types of arthritic diseases, such as how susceptible individuals are and the population types involved.
Approximately fifty percent of all sufferers from juvenile chronic arthritis fall into the oligoarticular type with few joints affected, making it the most common type. With a greater number of joints affected by arthritis, the polyarticular type occurs in about a third of patients, with the remaining patients having the systemic form. Juvenile arthritis patients may be susceptible to acquiring a second autoimmune disorder. The significant disability and pain causes psychological distress, problems with behaviour, depression and anxiety. Girls are more likely to suffer from the many joint affected and poor joint affected forms, with equal incidence in the systemic form.
There are two peaks of age occurrence in the many joint affected or polyarticular type of juvenile arthritis, at between 6 and 12 years and between 1 and 4 years. The fewer joint or oligoarticular form peaks between 2 and 4 years, with no particular pattern in age incidence for the systemic form. How the disease behaves over the first six months indicates which form of the disease the patient will be classed as. With a fewer affected joints form there will be four or less involved over this time period. The polyarticular type has five or more affected joints during the six months since onset. The systemic form does not have this pattern but its symptoms are rashes, arthritis and a fever.
If a diagnosis of juvenile arthritis of some form is to be made then the patient should have arthritis of some of their joints for at least six weeks. Stiffness in the morning or after periods when the joint has been kept still is a typical complaint. The start of the disease can be very sudden and dramatic or may come on slowly over some time, with common symptoms including stiffness of the joints as mentioned, joint pain in the day, periods of absence from school and a limping gait. Some patients also suffer from inflammatory disease of the bowel. A child may not always report actual pain in a joint but instead they may just allow the joint to go unused and develop atrophy or a joint contracture.
The type of juvenile chronic arthritis which has a system wide onset has typical symptoms of a fever which spikes regularly once or twice a day with the temperature going back towards normal in between the spikes. This is helpful diagnostically as infections do not behave in this way. A skin rash which lasts a few hours only may appear on the trunk and the limbs, the child may not be well and the larger joints may exhibit pain.
Author: Jonathan Blood-Smyth