title: Clinical and genetic associations of radiographic sacroiliitis and its different patterns in psoriatic arthritis.
abstract: OBJECTIVE
  We aimed to 1) identify clinical and genetic associations of sacroiliitis (SI) in patients with psoriatic arthritis (PsA), and 2) describe the different radiographic patterns of SI in PsA and their clinical and genetic associations.
  
  
  METHODS
  283 PsA patients, fulfilling CASPAR criteria, underwent detailed skin and rheumatologic assessments. In addition, HLA-B*27 and B*080101 status was recorded, which have been shown as the key genetic markers of radiographic SI in PsA. Grade 2 Unilateral or bilateral radiographic changes of SI were required for inclusion and involvement was further defined as asymmetrical or symmetrical.
  
  
  RESULTS
  70 patients (25%) had radiographic SI; all either with a present or past history of backache. Regression analysis demonstrated a significant association of SI with peripheral joint erosions (p=0.043), PASI maximum (p=0.041), younger age of PsA onset (p=<0.001), presence of HLA-B*0801 (p=0.002) and only marginal significance with HLA-B*2705 (p=0.059). Asymmetrical SI was noted in 51 patients (73%). In striking contrast to those patients with symmetrical SI, patients with asymmetrical SI were more likely to be female (p=0.04), have a trend towards more severe nail disease (p=0.08) and peripheral joint erosions (p=0.08), more osteolysis (p=0.01), more HLA-B*0801 positivity (p=0.001) and much less HLA-B*270502 positivity (p=<0.001).
  
  
  CONCLUSIONS
  PsA developing at a younger age, severe skin disease, peripheral joint erosions, and HLA-B*0801 are significantly associated with SI, and there was only a marginal trend towards significance for HLA-B*2705. HLA-B*27 positive Axial-PsA patients resemble AS, while HLA-B*0801 positive Axial-PsA patients have asymmetrical and/or unilateral SI, which are typical of PsA.
authors.affiliation: Department of Rheumatology, St Vincent's University Hospital, Dublin; and Division of Rheumatology, Department of Medicine, University Hospital Kerry, Ireland. mharoon301@hotmail.com.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Haroon
authors.affiliation: Division of Rheumatology, Columbia University, College of Physicians and Surgeons, New York, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Winchester
authors.affiliation: Division of Rheumatology, Columbia University, College of Physicians and Surgeons, New York, USA.
authors.forename: Jon T
authors.initials: JT
authors.lastname: Giles
authors.affiliation: Department of Diagnostic Imaging, St Vincent's University Hospital, Dublin, Ireland.
authors.forename: Eric
authors.initials: E
authors.lastname: Heffernan
authors.affiliation: Department of Rheumatology, St Vincent's University Hospital, Dublin, Ireland.
authors.forename: Oliver
authors.initials: O
authors.lastname: FitzGerald
mesh_terms: D000328:Adult; D017668:Age of Onset; D015535:Arthritis, Psoriatic / Q000000981:diagnostic imaging* / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D001416:Back Pain / Q000000981:diagnostic imaging / Q000235:genetics; D003430:Cross-Sectional Studies; D005260:Female; D056726:Genetic Association Studies; D005819:Genetic Markers; D020022:Genetic Predisposition to Disease; D015796:HLA-B27 Antigen / Q000235:genetics* / Q000276:immunology; D015795:HLA-B8 Antigen / Q000235:genetics* / Q000276:immunology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D011379:Prognosis; D012307:Risk Factors; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging* / Q000276:immunology; D058566:Sacroiliitis / Q000000981:diagnostic imaging* / Q000235:genetics* / Q000276:immunology; D012720:Severity of Illness Index; D012867:Skin / Q000473:pathology
chemical_list: D005819:Genetic Markers; C509422:HLA-B*08:01 antigen; D015796:HLA-B27 Antigen; D015795:HLA-B8 Antigen