Rheumatoid arthritis as an infectious disease

Association between rheumatoid arthritis and genetic variants of natural resistance-associated macrophage protein 1 gene: A meta-analysis

AIM

To evaluate the association between natural resistance-associated macrophage protein 1 (NRAMP1) polymorphisms and rheumatoid arthritis (RA).

METHOD

All related studies were retrieved and screened from PubMed, CNKI and Web of Science. Pooled odds ratios (ORs) and 95% CIs were assessed for the strength of association between NRAMP1 and RA. Publication bias was measured by Begg's funnel plot and Egger's regression test. The robustness of this meta-analysis was detected by sensitivity analysis.

RESULTS

A total of five eligible publications were included in the present meta-analysis. The polled data showed no association between RA and NRAMP1 D543N and 1729 + 55del4 in the allele model. However, the relationship between RA and NRAMP1 INT4 was statistically significant (OR 1.65, 95% CI 1.14-2.38). Genotypic analysis demonstrated that there were no associations between RA and NRAMP1 D543N, 1729 + 55del4 and INT4 in homozygous comparison (D543N: OR 0.97, 95% CI 0.15-6.09; 1729 + 55del4: OR 1.19, 95% CI 0.29-24.88; INT4: OR 3.18, 95% CI 0.62-16.26), dominant model (D543N: OR 1.04, 95% CI 0.61-61.78; 1729 + 55del4: OR 1.41, 95% CI 0.81-2.47; INT4: OR 1.22, 95% CI 0.72-2.06) and recessive model (D543N: OR 0.93, 95% CI 0.15-5.91; 1729 + 55del4: OR 0.99, 95% CI 0.26-3.86; INT4: OR 2.95, 95% CI 0.61-14.16). In heterozygous comparison, it no association was shown between RA and NRAMP1 D543N and INT4, excepting NRAMP1 1729 + 55del4 (OR 1.73, 95% CI 1.17-2.56). Further subgroup analysis indicated that NRAMP1 1729 + 55del4 and INT4 were related to RA in Asia and in the Hardy-Weinberg equilibrium group. There exists no publication bias in this meta-analysis.

CONCLUSION

This meta-analysis indicated that NRAMP1 1729 + 55del4 and INT4 confer susceptibility to RA.

Rheumatoid arthritis: Disease or syndrome?

Rheumatoid arthritis (RA) has been described in the medical literature for over two hundred years, but its etiology remains unknown. RA displays phenotypic heterogeneity, and it is a relatively prevalent clinical entity: it affects approximately 1% of the population, resulting in enormous pathologic sequelae. Earlier studies targeting the cause(s) of RA suggested potential infectious involvement, whereas more recent reports have focused on a genetic origin of the disease. However, neither infection nor genetics, nor any other single factor is currently accepted as causative of RA. In this article we review studies relating to the etiology of RA, and those of several related matters, and we conclude that the literature indeed does provide insight into the causes underlying the initiation of RA pathogenesis. Briefly, given the remarkable phenotypic variation of RA, especially in its early stages, as well as a number of other characteristics of the condition, we contend that RA is not a discrete clinical entity with a single etiological source. Rather, we argue that it represents a common clinical endpoint for various starting points, each of which is largely guided by as yet poorly understood aspects of the genetic background of the affected individual. Adoption of this alternative view of the origin of RA will have significant consequences for future research and for development of new therapeutic interventions for this burdensome condition.