[Clinical features of infantile patient with juvenile rheumatoid arthritis].

Little is known about clinical features of infantile juvenile rheumatoid arthritis (JRA) because it is very rare for the patients to develop JRA within one year of age. In the past 20 years, we experienced three JRA patients whose onset was under 1 year of age. The incidence of infantile JRA was 3.2% of all JRA patients in our facility. They are 9 month-old male with systemic onset, 6-month-old female with polyarticular onset and 8 month-old female with systemic onset. It was difficult to evaluate subjective symptoms such as arthralgia or morning stiffness since the patients could not complain precisely. Therefore, careful observation on their behaviors, such as the delayed development of their motor function and bad humor and/or loss of activity in the morning, was important for evaluating joint symptoms. In case 1, measuring the serum level of hyaluronic acid was specifically useful to evaluate the arthritis. Drug therapy was not successful especially in infantile JRA. One of the reason for this ineffectiveness of drug therapy might be explained by poor adsorption of drugs in infants; the serum acetyl salicylic acid level was lower in infantile patients than the other patients with JRA even though they received enough dose of aspirin. Infantile JRA was revealed to have specific difficulties in early diagnosis and adequate treatment. Therefore, accumulated case studies about clinical features of infantile JRA is essential for their better prognosis.