RESUMO
The discovery of unique autoantibodies has informed and altered our approach to the diagnosis and management of the inflammatory myopathies. This study reports the initial clinical experience of use of the Extended Myositis Antibody (EMA) panel in the largest university teaching hospital in Ireland. We conducted a retrospective review of all patients who had serum samples tested for myositis specific antibodies and myositis associated antibodies from April 2014 to March 2015. A positive EMA panel was of significant clinical utility in facilitating decisions on appropriate investigations, and need for onward referral to other physicians. Furthermore, this paper highlights the diversity of possible presentations of idiopathic inflammatory myopathy with subsequent need for multi-speciality involvement, and serves to heighten awareness among clinicians of the diagnostic use of extended myositis antibody testing in these cases.
RESUMO
OBJECTIVE: We have previously identified a single-nucleotide polymorphism (SNP) haplotype involving the lymphotoxin alpha (LTA) and tumor necrosis factor (TNF) loci (termed haplotype LTA-TNF2) on chromosome 6 that shows differential association with rheumatoid arthritis (RA) on HLA-DRB1*0404 and *0401 haplotypes, suggesting the presence of additional non-HLA-DRB1 RA susceptibility genes on these haplotypes. To refine this association, we performed a case-control association study using both SNPs and microsatellite markers in haplotypes matched either for HLA-DRB1*0404 or for HLA-DRB1*0401. METHODS: Fourteen SNPs lying between HLA-DRB1 and LTA were genotyped in 87 DRB1*04-positive families. High-density microsatellite typing was performed using 24 markers spanning 2,500 kb centered around the TNF gene in 305 DRB1*0401 or *0404 cases and 400 DRB1*0401 or *0404 controls. Single-marker, 2-marker, and 3-marker minihaplotypes were constructed and their frequencies compared between the DRB1*0401 and DRB1*0404 matched case and control haplotypes. RESULTS: Marked preservation of major histocompatibility complex haplotypes was seen, with chromosomes carrying LTA-TNF2 and either DRB1*0401 or DRB1*0404 both carrying an identical SNP haplotype across the 1-Mb region between TNF and HLA-DRB1. Using microsatellite markers, we observed two 3-marker minihaplotypes that were significantly overrepresented in the DRB1*0404 case haplotypes (P = 0.00024 and P = 0.00097). CONCLUSION: The presence of a single extended SNP haplotype between LTA-TNF2 and both DRB1*0401 and DRB1*0404 is evidence against this region harboring the genetic effects in linkage disequilibrium with LTA-TNF2. Two RA-associated haplotypes on the background of DRB1*0404 were identified in a 126-kb region surrounding and centromeric to the TNF locus.
Assuntos
Artrite Reumatoide/genética , Antígenos HLA/genética , Haplótipos , Estudos de Casos e Controles , Cromossomos Humanos Par 6/genética , Predisposição Genética para Doença , Genótipo , Antígenos HLA/classificação , Antígenos HLA-DR/genética , Cadeias HLA-DRB1 , Humanos , Desequilíbrio de Ligação , Linfotoxina-alfa/genética , Repetições de Microssatélites , Polimorfismo de Nucleotídeo Único , Fator de Necrose Tumoral alfa/genéticaRESUMO
Following the successful determination of the molecular genetics of single-gene disorders, attention has not surprisingly turned to complex genetic disorders. However, preliminary experience suggests that unravelling the genetic component of common inflammatory disorders, such as rheumatoid arthritis, multiple sclerosis and systemic lupus erythematosus, might be a harder nut to crack.
