Fator reumatóide IgE na artrite reumatóide juvenil

Abstract

Juvenile Rheumatoid Arthritis (JRA) is a chronic inflammatory disease whose pathogenic mechanism is still unclear. The clinical manifestations of this disease result from a series of multifactorial events involving mechanisms dependent on B and T cells. The IgM Rheumatoid Factor (FR-lgM) detected by the latex agglutination technique occurs in 5% to 10% of patients with JRA and it is associated with progression to erosive and disabling disease. Some studies show that other RF isotypes (IgA, IgG and IgE) may be present in this disease, although its clinical and prognostic value remains unknown. The objectives of the present study were: to determine the presence of FR-IgE in the FYR and correlate it with prognostic factors. A prospective multicenter study was carried out between January 1993 and January 1999 with the participation of three pediatric freumatology centers (Faculty of Medicine, University of São Paulo, Ribeirão Preto School of Medicine, University of São Paulo and Federal University of Uberlândia ). 91 children diagnosed with FRA were studied according to the criteria of the American College of Rheumatology: 38 (42%) with the systemic onset, 28 (31%) pauciarticular and 25 (27%) polyarticular. The average age was 10 years and 6 months, with a range from 2 years and 1 month to 22 years and 7 months and 59 (65%) children were female. The control group consisted of 45 healthy children. The detection of FR-lgE was performed through an immunoenzymatic assay (ELISA). Mouse IgG was used to sensitize microplates and, as a conjugate, human anti-IgE labeled with peroxidase. For each reaction, the cut-off value was established according to the average of the optical densities of the negative controls plus three standard deviations. In order to avoid possible intra- and inter-assay variations, a correction factor was established to express the results in terms of the ELISA index. FR-lgE was correlated with: FR-lgM (latex), total serum IgE, ESR, ANA, functional and radiological class III or IV. Of the 91 children with JRA, 15 (16.5%) had positive FR-IgE. Of these, 7 (18.5%) in the systemic form, 5 (18%) in the pauciarticular and 3 (12%) in the polyarticular. There was a statistically significant correlation between FR-lgE and: geometric mean of total serum IgE in the total of patients with JRA and positivity of FR-lgM (latex) in patients with the polyarticular shape (p = 0.0312). There was no statistical correlation between FR-IgE and functional and radiological class III or IV in any form of disease onset. Of the 45 controls, 5 (11%) also showed positive FR-IgE, but there was no correlation with total serum IgE. In conclusion, FR-lgE can be detected in 16.5% of patients with JRA, especially in those with high levels of total serum IgE. The presence of FR-lgE in patients with polyarticular shape is also generally correlated with positivity for FR-lgM (latex). FR-lgE does not seem to be associated with a worse prognosis for JRA.