Purpose of review: We review our current knowledge about the clinical features of patients with ankylosing spondylitis (AS) who possess HLA-B*27 versus those who lack this gene.
Recent findings: ERAP1 association is present only in HLA-B*27+ patients, but other genetic associations are similar between the two groups. A genetic study supports the existence of an HLA-B27-independent common link between gut inflammation and AS. It is unusual to observe familial occurrence of primary AS among families of northern European extraction that show no segregation of HLA-B*27, psoriasis, or IBD. Although there are many similarities among AS patients possessing HLA-B*27 versus those lacking this gene, the former group has a younger age of onset, a shorter delay in diagnosis, a better clinical response to tumor necrosis factor inhibitors, a greater familial occurrence, a greater risk for occurrence of acute anterior uveitis, and a lower risk for occurrence of psoriasis and IBD. ERAP1 association is present only in HLA-B*27+ patients, but other genetic associations are similar between the two groups. It is unusual to observe occurrence of primary AS among families of northern European extraction that show no segregation of HLA-B*27, IBD, or psoriasis. A recent genetic study supports the existence of an HLA-B*27-independent common link between gut inflammation and AS.
Keywords: Ankylosing spondylitis; Clinical features; ERAP1; Familial occurrence; Genetic susceptibility; HLA-B*27; HLA-B27; Inflammatory bowel disease; Psoriasis; Spondyloarthritis; Uveitis.