To evaluate the relative contribution of the human leukocyte antigen (HLA)-B27 to psoriatic spondyloarthropathy (PsSpA) susceptibility and to analyze whether this antigen contributes to disease expression.
This cross-sectional study included 70 patients (mean age 48 +/- 14.5 years; 44 men and 26 women). PsSpA was defined according to radiological findings (grade 2 or more sacroiliitis), and patients were classified into 3 main subtypes: isolated axial disease (n = 16), axial plus oligoarthritis (n = 29) and axial plus polyarthritis (n = 25). All patients were studied following a standard protocol that included the collection of demographic and epidemiological data, clinical history, radiographs, complementary tests, physical examination, and HLA-B27 testing (serological method). For functional evaluation, the Health Assessment Questionnaire-Specific for spondyloarthropathy (HAQ-S) was used. Patients with and without HLA-B27 antigen were compared on the basis of the data.
Twenty-four patients (34%) carried the HLA-B27 antigen (RR 6.4, P <.0004). Fifty-six percent of those patients with the isolated axial pattern had this antigen, compared with 24% in the poly-arthritis axial pattern and 31% of those in the oligo-arthritis axial group (P =.016). Univariate analysis demonstrated correlations between HLA-B27 and an earlier age of onset for both psoriasis (P =.028) and arthritis (P =.006), male gender (P =.002), bilateral sacroiliitis (P =.002), and uveitis (P =.026). HLA-B27 negative patients developed more peripheral erosions than HLA-B27 positive patients (P =.05). No correlation was found between B27 and clinical symptoms of back involvement, syndesmophytes, or functional impairment.
The HLA-B27 antigen is not only important for PsSpA susceptibility, but also determines some clinical features. This antigen was associated with earlier age of psoriasis and arthritis onset, bilateral sacroiliitis, and male gender. However, it was not associated with either the severity or extension of the spondylitic process or with functional impairment.