Increasing levels of human leukocyte antigen (HLA)-B*27 are linked to more severe sonographic enthesitis in patients with psoriatic arthritis (PsA), according to a study published in Arthritis & Rheumatology.

Among human leukocyte antigen genes, the allele HLA-B*27 correlated with more severe enthesitis among patients with psoriatic arthritis, which suggests that genetic variants can affect an individual’s predisposition to sub-phenotypes of psoriatic arthritis.

“Among the genetic risk factors, [human leukocyte antigen (HLA)] class I genes have been associated with the highest risk of developing PsA,” Ari Polachek, of Toronto Western Hospital and Tel Aviv University, and colleagues wrote.

“Within this group, the following HLA B alleles have been associated with PsA: HLA B*27, B*08:01, B*38:01, B*39:01, while HLA C*06:02 has been associated with psoriasis.”

According to Polachek and colleagues, HLA alleles, particularly HLA B*27, also correlate with PsA sub-phenotypes.

“However, there is limited information regarding the association between HLA risk alleles for PsA and enthesitis,” they wrote. “Investigating this link could elucidate the role of genetic factors in the development of the various sub-phenotypes of PsA.”

To analyze the association between six genetic susceptibility markers related to HLA and sonographic enthesitis in PsA, the researchers conducted a cross-sectional study of 225 patients at the University of Toronto.

The researchers used the Madrid Sonography Enthesitis Index (MASEI) to assess sonographic enthesitis, and sequence-specific oligonucleotide probes for genotyping.

Additionally, they performed multivariable regression models adjusted for age, sex, BMI and disease duration to determine associations between PsA susceptibility markers and enthesitis severity.

According to the researchers, HLA-B*27 (beta = 4.24; 95% CI, 0.02-8.46) correlated with a higher enthesitis score. Further, the interaction between HLA-B*27 and PsA duration was statistically significant.

According to Polachek and colleagues, this demonstrated an increasing effect of HLA-B*27 with longer PsA duration (beta = 4.62; 95% CI, 1.38-7.86).

“The results of this study suggest that HLA-B*27 is associated with the extent of enthesitis in patients with PsA,” Polachek and colleagues wrote.

“The effect of this allele on the extent sonographic enthesitis increases with longer disease duration which represents the accumulation of bony entheseal damage over time. These findings highlight the potential genetic predisposition of enthesitis and the importance of certain HLA alleles in determining PsA sub-phenotypes” authors concluded.