Objective: Amyloidosis is an important severe complication of rheumatoid arthritis (RA). The study was designed to evaluate polymorphism of the gene encoding serum amyloid A as well as Chlamydia trachomatis infection as risk factors of development of amyloidosis in RA patients.
Material and methods : One-hundred and four patients with definite RA were investigated. The patients were divided into two groups, the AA-positive group (secondary amyloidosis confirmed by histopathological evaluation of the tissue sample) (45 patients), and the AA-negative group (59 patients).
The polymorphism of SAA1 and occurrence of Chlamydia trachomatis infection were assayed in all the patients.
Results: No significant differences between the two patient groups in the -13T/C allele frequency were revealed. Therefore, the -13T allele is not obligatory for AA amyloidosis development in Belarusian patients with RA. Comparison of groups for genotype and three allele frequencies showed statistically significant differences. The most notable differences were observed in SAA1 α/α genotype –c2 = 31.1 (p < 0.001). Forty-three of 45 AA-positive RA patients (96%) had SAA1 a/a genotype while only 32% AA-negative RA patients presented this genotype. A similar tendency was observed for allele a frequency: c2 = 47.01 (p < 0.001).
Up to 84% of 45 AA-positive RA patients had concomitant Chlamydia trachomatis infection during the course of RA. In the
AA-negative group association of RA and the infection was revealed in 10 (17%) of 59 patients only (p < 0.004).
The odds ratio (OR) calculated for the SAA1 a/a genotype was 45.26, and the 95% confidence interval (95% CI) was 9.9–206.8. Odds ratio for Chlamydia trachomatis infection was 26.6 (95% CI: 9.26–76.37).
Conclusion: Risk of secondary amyloidosis in RA patients significantly depends on SAA1 genotype and the presence of Chlamydia trachomatis infection.