Association of STAT4 and BLK, but not BANK1 or IRF5, with primary antiphospholipid syndrome.
OBJECTIVE
Primary antiphospholipid syndrome (APS) is formally classified by the presence of antiphospholipid antibodies, recurrent thrombosis, and/or pregnancy morbidity in the absence of any underlying full-blown systemic autoimmune disease. However, systemic manifestations in patients with primary APS have been recently reported, as has the presence of serologic markers in common with systemic lupus erythematosus (SLE). In spite of similarities between the 2 diseases, only a minority of cases of primary APS evolve into full-blown SLE, even after a long followup period. The aim of this study was to investigate whether the analysis of SLE susceptibility genes may provide at least a partial explanation for such a discrepancy.


METHODS
One hundred thirty-three patients with primary APS classified according to the Sydney criteria and 468 healthy control subjects from the same geographic area were recruited. We genotyped 3 single-nucleotide polymorphisms (SNPs) in IRF5 (rs2004640, rs2070197, and rs10954213), 4 SNPs in STAT4 (rs1467199, rs3821236, rs3024866, and rs7574865), 2 SNPs in BANK1 (rs10516487 and rs3733197), and 1 SNP in BLK (rs2736340).


RESULTS
STAT4 and BLK displayed a strong genetic association with primary APS (for rs7574865, odds ratio [OR] 2.19, P=5.17x10(-7); for rs2736340, OR 2.06, P=1.78x10(-6)), while a weak association with IRF5 and no association with BANK1 were observed.


CONCLUSIONS
The presence of a strong genetic association with only a few SLE susceptibility genes and the absence of a more complex gene association may contribute to the lack of cases of full-blown SLE developing in patients with primary APS, in spite of the clinical and serologic similarities between SLE and primary APS.
Yin
Hong
H
Department of Genetics and Pathology, Uppsala University, Uppsala, Sweden.
Borghi
Maria Orietta
MO
Delgado-Vega
Angélica M
AM
Tincani
Angela
A
Meroni
Pier-Luigi
PL
Alarcón-Riquelme
Marta E
ME
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D017152:Antibodies, Antiphospholipid / Q000097:blood; D016736:Antiphospholipid Syndrome / Q000235:genetics* / Q000276:immunology; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D050835:Interferon Regulatory Factors / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D012307:Risk Factors; D050797:STAT4 Transcription Factor / Q000235:genetics*; D019061:src-Family Kinases / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; D017152:Antibodies, Antiphospholipid; C447641:BANK1 protein, human; C431713:IRF5 protein, human; D050835:Interferon Regulatory Factors; D008565:Membrane Proteins; D050797:STAT4 Transcription Factor; C494090:STAT4 protein, human; C082599:protein-tyrosine kinase p55(blk); D019061:src-Family Kinases