Exploring the phenotypic expression of HLA-B27 in psoriatic arthritis

Psoriatic arthritis (PsA) is a heterogeneous inflammatory disease within the spectrum of spondyloarthritis (SpA) that shares genetic and clinical features with other subtypes. HLA-B27 is a well-established genetic risk allele for axial SpA, while its role in PsA is less clear. This study aimed to investigate the association between HLA-B27 and the clinical, laboratory, and therapeutic features of a real-world PsA cohort.

We performed a retrospective analysis of 333 patients with PsA who fulfilled the CASPAR criteria and had documented HLA-B27 status. Demographic, clinical, laboratory, and treatment-related data were extracted from medical records. Patients were compared based on HLA-B27 positivity using appropriate statistical analyses. Statistical significance was set at p < 0.05.

HLA-B27 was positive in 11.7% of patients. Compared with HLA-B27-negative individuals, HLA-B27-positive patients showed significantly earlier PsA onset (42.8 vs. 49.1 years, p = 0.003), more frequent axial involvement (46.2% vs. 24.5%, p = 0.004), and higher prevalence of enthesitis (33.3% vs. 18.4%, p = 0.028). CRP levels were also higher in HLA-B27-positive patients (median 5.5 vs. 3.2 mg/L, p = 0.015). No significant differences were observed in sex, dactylitis, uveitis, treatment response, comorbidities, or frequency of difficult-to-treat and treatment-refractory disease between the two groups. Interestingly, HLA-B27 negativity was associated with higher FIB-4 scores (p = 0.034), a marker of hepatic fibrosis.

HLA-B27 is associated with a distinct clinical phenotype in PsA, including earlier onset, axial disease, enthesitis, and elevated systemic inflammation. These findings highlight the relevance of HLA-B27 in PsA stratification and support its role in identifying disease profiles. Key Points • HLA-B27 positivity was associated with an earlier PsA onset, axial involvement, and enthesitis. • Elevated CRP levels in HLA-B27-positive patients suggest increased systemic inflammation in this profile. • HLA-B27 status did not significantly affect the treatment response, comorbidities, or frequency of difficult-to-manage/refractory PsA. • HLA-B27 may help in the clinical stratification of PsA patients.