Increasing levels of human leukocyte antigen (HLA)-B27 are associated with more severe sonographic enthesitis in patients with psoriatic arthritis (PsA), according to a study published in Arthritis & Rheumatology.
In a cohort of 225 patients with PsA, investigators assessed the association between 6 HLA alleles and the severity of sonographic enthesitis. The frequencies of the alleles were as follows: B27, 15.6%; B38:01, 18.2%; B39:01, 4.9%; B44:02/B44:03, 21.3%; B08:01, 16.9%; and C06:02, 27.6%. Investigators used sequence-specific oligonucleotide probes for HLA genotyping and relied on the Madrid Sonography Enthesitis Index (MASEI) scoring system to assess for enthesitis in a cross-sectional analysis. All analyses were adjusted for age, body mass index, disease duration, and sex.
At baseline, the average PsA duration of study participants was 16.9±12.3 years, and approximately half (53.6%) of patients were being treated with conventional disease-modifying antirheumatic drugs (DMARDs) and biologics. Compared with the other HLA markers, HLA-B27 was associated with a significantly higher sonographic enthesitis score (β =4.24; 95% CI, 0.02-8.46). Conversely, the HLA-C06:02 allele was associated with a lower enthesitis score (β = −4.11; 95% CI, −7.73 to −0.50). In addition, the investigators observed an increasing effect of HLA-B27 with greater duration of PsA (β =4.62; 95% CI, 1.38-7.86). Participants’ body mass index was a significant predictor for higher MASEI score (β, 0.35; 95% CI, 0.20-0.49).
The investigators suggested that the assessed sonographic lesions could have changed as a result of treatment, yet these changes were not adjusted for in the analysis. In addition, the researchers added that the findings may not be generalizable to patients with short-standing PsA or to patients who are not being treated with biologic or nonbiologic DMARDs.
Researchers noted that the “effect of [the HLA-B27] allele on the extent sonographic enthesitis increases with longer disease duration which represents accumulation of bony entheseal damage over time.”
Polachek A, Cook R, Chandran V, et al. The association between HLA genetic susceptibility markers and sonographic enthesitis in psoriatic arthritis [published online January 23, 2018]. Arthritis Rheumatol. doi:10.1002/art.40423