Aches and pains in children are common and usually short lived. There are criteria for rheumatic fever, while the adult criteria for dermatomyositis and systemic lupus erythematosus, somewhat modified for the young, are well accepted, but an international classification of chronic arthritis in children is only just being developed. The Task Force meeting of 1997 is currently in press. The international name is now “Juvenile Idiopathic Arthritis” and requires the patient to be under 16 years of age at onset and have arthritis of unrecognised aetiology for a minimum of 6 weeks. The aim is to put together clinically homogenous groups at presentation: systemic arthritis, oligoarthritis–persistent and extended-polyarthritis rheumatoid factor negative, polyarthritis rheumatoid factor positive, psoriatic arthritis, enthesitis related arthritis and others. This last includes arthritis which fits no other category or more than one category. For each group there is a definition descriptor and list of exclusions.
In the United Kingdom the prevalence of juvenile idiopathic arthritis as a database has shown annual incidence rates from two large districts similar at 10 per 100,000 children under 16.
Systemic arthritis. In Europe this accounts for some 11-14%. The peak age of onset is about 2 years, but it can begin even before the first birthday. There is no difference in frequency between boys and girls. Diagnosis rests on the presence of the daily high spiking fever, transient maculopapular rash and arthritis. Other clinical features include serositis, hepatosplenomegaly and lymphadenopathy. Needless to say many childhood illnesses can mimic, particularly infections such as parvovirus, also neoplasms such as leukaemia and neuroblastoma, Kawasaki disease, periodic fever and hyper IgD syndrome. Very occasionally a primary vasculitis or systemic lupus erythematosus may give problems in diagnosis. Investigations will show a very high ESR and C-reactive protein with high white cells and thrombocytes. The persistence of sever thrombocytosis goes with a prolonged course. Systemic onset features are followed by polyarthritis which becomes more prominent as time passes and the systemic features tend to regress over 3 to 4 years, but such patients will often have flare-ups during intercurrent infections; rhinovirus, herpes simplex and streptococcus have all been identified as triggers.
Oligoarthritis. In this there are 4 or fewer joints, girls affected around the age of 3 or 4 are particularly common; it can be associated with chronic uveitis. The presence of antinuclear antibodies is a marker for uveitis, but the association is not exclusive. The most commonly involved joints are knees, ankles with hind foot and elbow involvement, it will probably be in an asymmetrical pattern to begin with. In extended oligoarthritis, while the children have an onset with less than 4 joints, over a year or two they start to spread in an asymmetrical way and continue to have progressive joint involvement and deterioration in function.
Polyarthritis. Polyarticular disease can be of two types. More commonly it is negative for rheumatoid factor, but a small proportion of patients are rheumatoid factor positive. This last group generally occurs about the teenage and for them the prognosis is poor with rapid widespread joint destruction unless put onto appropriate therapy early. This particular group accounts for a large number of total joint replacements performed in the young adult era. Seronegative polyarthritides are poorly defined with probably several subgroups including which predominantly has stiffness and joint contractures without very much overt synovitis.
Enthesitis arthritis. This is what used to be called juvenile spondyloarthropathy. The clinical features are asymmetrical arthritis of the lower limb joints and enthesitis affecting particularly boys, either pre-teen or teenage. Acute anterior uveitis can occur in this group; such patients carry HLA B27. It is only rarely that sacroiliitis occurs early, but may follow at a later date.
Juvenile Psoriatic arthritis. There has now been consensus on the pattern of joint involvement with single fingers or toes with joint and tendon involvement leading to a sausage shape, with polyarthritis often affecting the larger joints associated with actual psoriasis, nail pitting or a family history of psoriasis.
Presently, although these different types have been outlined clinically, and some genetic factors have been sorted out, much work remains to be done including assessing those patients who do not fit the criteria.
Management. This will depend on the pattern of illness present. Thus in systemic onset disease it may be fully justified to start off with intravenous Methylprednisone and then go on to oral steroids associated with a good non-steroidal regime. No slow acting drug has been found to be particularly helpful and Gold and Sulphasalazine may well be contra-indicated because their high incidence of toxicity in this group. Methotrexate can be used once there is polyarthritis, but those who start with systemic illness do not seem to do as well as other subgroups. The role of Hydroxychloroquine has not been fully explored. For seropositive polyarthritis both Gold and Methotrexate are valuable drugs, but need to be started early, given in adequate dose and continued as long as disease activity persists. Sometimes a polyarthritic child will be unwell, then it is justifiable to put a low dose of corticosteroid on alternate days, preferably Deflazacort because of its calcium sparing properties, and allowing growth to continue, as well as the slow acting drug such as Methotrexate. For the arthritis associated with HLA B27, Sulphasalazine in appropriate dosage appears to be the most valuable, but formal studies with Methotrexate have not been undertaken. Methotrexate also appears to be particularly valuable in the psoriatic subgroup.
Drugs are only part of management. Information to the parents about the disease and to the children when older is essential. Joint function must be maintained by appropriate use of splints either for rest or rest and work, insoles to support the feet in good position and for an active exercise regime to maintain joint and muscle function. This will need to be done at home, and must be supervised or bad habits develop. This is particularly important because young people who have had juvenile arthritis can experience isolation, depression and despite above average educational achievements, greater unemployment.
There is much work is going on with regard to genetic patterns and possible triggers. It is important that the new classification is used so that research workers the world over look at the same type of children in their studies. There may well be racial difference in the genetic markers; these will include not only the histocompatibility complex which has been studied and also the role of different cytokines which can be broadly divided into pro-inflammatory ie., Interleukin 1 and 12 and anti-inflammatory Interleukins IL-10 and 13.
