The effect of HLA-DR on susceptibility to rheumatoid arthritis is influenced by the associated lymphotoxin α-tumor necrosis factor haplotype

Objective. HLA-DRB1, a major genetic determinant of susceptibility to rheumatoid arthritis (RA), is located within 1,000 kb of the gene encoding tumor necrosis factor (TNF). Because certain HLA-DRB1*04 subtypes increase susceptibility to RA, investigation of the role of the TNF gene is complicated by linkage disequilibrium (LD) between TNF and DRB1 alleles. By adequately controlling for this LD, we aimed to investigate the presence of additional major histocompatibility complex (MHC) susceptibility genes. Methods. We identified 274 HLA-DRB1*04-positive cases of RA and 271 HLA-DRB1*04-positive population controls. Each subject was typed for 6 single-nucleotide polymorphisms within a 4.5-kb region encompassing TNF and lymphotoxin a (LTA). LTA-TNF haplotypes in these unrelated individuals were determined using a combination of family data and the PHASE software program. Results. Significant differences in LTA-TNF haplotype frequencies were observed between different subtypes of HLA-DRB1*04. The LTA-TNF haplotypes observed were very restricted, with only 4 haplotypes constituting 81% of all haplotypes present. Among individuals carrying DRB1*0401, the LTA-TNF 2 haplotype was significantly underrepresented in cases compared with controls (odds ratio 0.5 [95% confidence interval 0.3-0.8], P = 0.007), while in those with DRB1*0404, the opposite effect was observed (P = 0.007). Conclusion. These findings suggest that the MHC contains genetic elements outside the LTA-TNF region that modify the effect of HLA-DRB1 on susceptibility to RA.

Genetics and genomics of ankylosing spondylitis

Ankylosing spondylitis (AS) is a common, highly heritable arthropathy, the pathogenesis of which is poorly understood. The mechanism by which the main gene for the disease, HLA-B27, leads to AS is unknown. Genetic and genomic studies have demonstrated involvement of the interleukin-23 (IL-23) signaling pathway in AS, a finding which has stimulated much new research into the disease and has led to therapeutic trials. Several other genes and genetic regions, including further major histocompatibility complex (MHC) and non-MHC loci, have been shown to be involved in the disease, but it is not clear yet how they actually induce the condition. These findings have shown that there is a strong genetic overlap between AS and Crohn's disease in particular, although there are also major differences in the genes involved in the two conditions, presumably explaining their different presentations. Genomic and proteomic studies are in an early phase but have potential both as diagnostic/prognostic tools and as a further hypothesis-free tool to investigate AS pathogenesis. Given the slow progress in studying the mechanism of association of HLA-B27 with AS, these may prove to be more fruitful approaches to investigating the pathogenesis of the disease. © 2009 John Wiley & Sons A/S.

HLA-DR/DQ haplotype in rheumatoid arthritis: Novel allelic associations in UK Caucasians

Objective. To elucidate the relative importance of the HLA-DR and HLA-DQ loci in conferring genetic predisposition to rheumatoid arthritis (RA). Methods. HLA-DRB1 and HLA-DQB1 alleles were typed in a set of 685 patients with RA using sequence-specific polymerase chain reaction. Allele and phenotype frequencies were compared with those in 2 large sets of historical, ethnically matched healthy controls, using the relative predispositional effect method. Results. Positive association was confirmed with the shared epitope positive HLA-DRB1 alleles associated with RA in Caucasians. A significant susceptibility effect was observed with HLA-DRB1*09, described in other ethnically diverse populations but not in Caucasians. A significant underrepresentation of the HLA-DRB1*0103 variant was noted among the RA cases, supporting the proposed protective role of the DERAA motif at residues 70-74 of the DR�� molecule. No HLA-DRB1 independent association of the HLA-DQB1 alleles, implicated in predisposing to RA, was evident. Conclusion. These data corroborate the shared epitope hypothesis of susceptibility to RA and provide strong evidence for the DRB1 locus as the primary RA susceptibility factor in the HLA region.

How do Australian podiatrists manage patients with diabetes The Australian diabetic foot management survey

Background Diabetic foot complications are the leading cause of lower extremity amputation and diabetes-related hospitalisation in Australia. Studies demonstrate significant reductions in amputations and hospitalisation when health professionals implement best practice management. Whilst other nations have surveyed health professionals on specific diabetic foot management, to the best of the authors’ knowledge this appears not to have occurred in Australia. The primary aim of this study was to examine Australian podiatrists’ diabetic foot management compared with best practice recommendations by the Australian National Health Medical Research Council. Methods A 36-item Australian Diabetic Foot Management survey, employing seven-point Likert scales (0 = Never; 7 = Always) to measure multiple aspects of best practice diabetic foot management was developed. The survey was briefly tested for face and content validity. The survey was electronically distributed to Australian podiatrists via professional associations. Demographics including sex, years treating patients with diabetes, employment-sector and patient numbers were also collected. Chi-squared and Mann Whitney U tests were used to test differences between sub-groups. Results Three hundred and eleven podiatrists responded; 222 (71%) were female, 158 (51%) from the public sector and 11–15 years median experience. Participants reported treating a median of 21–30 diabetes patients each week, including 1–5 with foot ulcers. Overall, participants registered median scores of at least “very often” (>6) in their use of most items covering best practice diabetic foot management. Notable exceptions were: “never” (1 (1 – 3)) using total contact casting, “sometimes” (4 (2 – 5)) performing an ankle brachial index, “sometimes” (4 (1 – 6)) using University of Texas Wound Classification System, and “sometimes” (4 (3 – 6) referring to specialist multi-disciplinary foot teams. Public sector podiatrists reported higher use or access on all those items compared to private sector podiatrists (p < 0.01). Conclusions This study provides the first baseline information on Australian podiatrists’ adherence to best practice diabetic foot guidelines. It appears podiatrists manage large caseloads of people with diabetes and are generally implementing best practice guidelines recommendations with some notable exceptions. Further studies are required to identify barriers to implementing these recommendations to ensure all Australians with diabetes have access to best practice care to prevent amputations.