The distribution of HLA-B27 subtype in patients with ankylosing spondylitis in Northern Norway

Although the high prevalence of human leucocyte antigen (HLA)-B27 and ankylosing spondylitis (AS) in Northern Norway is now well documented, data on the distribution of HLA-B27 subtypes and their potential impact on disease presentation and course are lacking.

We conducted a cross-sectional study of patients (n = 124) with established (modified New York criteria) AS participating in a longitudinal disease registry. Clinical data at the time of sample collection were recorded and genotyping for HLA-B27 was performed by low-resolution polymerase chain reaction (PCR) screening. Subtyping was then performed with sequence-specific primers (PCR-SSP) and direct exon 2 and 3 sequencing. The results were analysed with SCORE and Seqscape software.

Four patients (3%) were HLA-B27 negative in all genetic analyses. In the remaining 120 HLA-B27-positive patients, HLA-B27*05 was present in 117 (98%) and HLA-B27*02 in three patients (2%). There was complete concordance between the screening and subtyping results. The three patients with HLA-B27*02 had no distinguishing clinical characteristics.

HLA-B27*05 is the predominant subtype of HLA-B27 in Northern Norway. This supports the concept of a North-South gradient for HLA-B27 subtypes with little regional drive to adapt to environmental challenges. Low-resolution HLA-B27 PCR screening captures all relevant subtypes in this region.