Allelic and haplotypic HLA analysis in patients with psoriatic arthritis: Low frequency of common alleles

Introduction: Psoriatic arthritis is a complex disease, and human leukocyte antigens (HLA) are key to its development. Latin America and, specifically, Colombia, has scarce data about patients with psoriatic arthritis.
Objective: To describe the genotypic, allelic and haplotypic frequency of HLA alleles in psoriatic arthritis and associate them with clinical variables.
Materials and Methods: We conducted a retrospective study involving adult patients with psoriatic arthritis, evaluated according to CASPAR criteria, between 2012 and 2023. We included healthy donors whose HLA-A, B, C, and DR were genotyped by PCR/SSO in a Luminex 100/200 xMAP™ device. We performed an HLA comparative analysis between healthy donors and psoriatic arthritis patients.
Results: We included 401 healthy controls and 37 patients with psoriatic arthritis, in which we identified 46 genotypes, 75 alleles, and 32 haplotypes. The most frequent HLA were HLA-A*24 (37.1%), HLA-B*35 (20.8%), HLA-C*3 and HLA-C*7 (19.9% each), and HLADR* 4 (30%). Compared to healthy donors, the patient’s genotypic frequency was lower for HLA-A*02, HLA-A*11, HLA-B*35, HLA-DR*01, HLA-DR*07, HLA-DR*13, and HLA-DR*15 (p < 0.05), which means that even though HLA-B*35 was frequent in psoriatic arthritis, it's frequency was lower when compared to that of healthy controls. The frequency of HLA-A*24 and HLA-B*44 was different in cutaneous involvement (p < 0.05), HLA-B*40 and HLA-B*35 in joint involvement (p < 0.05), and HLA-A*26 and HLA-C*16 in extra-articular manifestations (p < 0.05). The allelic frequency of HLA-A*26:01 and HLA-C*16:01 in extra-articular manifestations was also significant. The frequency of HLA-Cw*6 was 6.7% and the allele HLA-B*27 was absent.
Conclusions: The HLA analysis in psoriatic arthritis showed a low frequency of HLA-C*06 and absence of HLA-B*27, different from the information reported for Caucasian population. These results also revealed other alleles of interest. Found differences could be related to the important racial mixing of our population.