What does HLA-B*27 mean for Ankylosing Spondylitis?

HLA-B27 is present in >90% of ankylosing spondylitis (AS) patients. However, only ~5% of HLA-B27 carriers develop AS. If experiencing chronic lower back pain (especially inflammatory pattern: worse at rest, improves with exercise, morning stiffness >30 min), consider rheumatology evaluation.

What does HLA-B*27 mean for Reactive Arthritis?

HLA-B27 carriers have increased susceptibility to reactive arthritis following certain infections (Chlamydia, Salmonella, Shigella, Yersinia).

What does HLA-B*27 mean for Anterior Uveitis?

HLA-B27 is associated with acute anterior uveitis. If experiencing sudden eye pain, redness, or light sensitivity, seek ophthalmologic evaluation promptly.

Learn · Pharmacogenomics

HLA-B*27

Ankylosing Spondylitis Susceptibility and 2 other associations.

Curated from CPIC / guidelines

What is HLA-B*27?

HLA-B*27 is a variant of a human leukocyte antigen (HLA) gene, the system the immune system uses to present fragments of proteins — including drugs bound to proteins — to T cells. Particular HLA alleles bind particular drugs, which is why carrying one can turn an ordinarily safe medicine into a severe immune reaction, and why some alleles track autoimmune conditions.

HLA-B27 is one of the most clinically significant HLA alleles. It is routinely tested in clinical practice for suspected spondyloarthropathies.

How common is HLA-B*27?

European	8.0%
East Asian	6.0%
African	2.0%
Global	6.0%

Conditions linked to HLA-B*27

Ankylosing Spondylitis Susceptibility high risk: HLA-B27 is present in >90% of ankylosing spondylitis (AS) patients. However, only ~5% of HLA-B27 carriers develop AS. If experiencing chronic lower back pain (especially inflammatory pattern: worse at rest, improves with exercise, morning stiffness >30 min), consider rheumatology evaluation.
Evidence: GWAS OR ~50-100; strongest known HLA-disease association · Source: IGAS Consortium; Nature Genetics 2010 · HLA-B27 prevalence: ~6-8% in Europeans, ~4-8% in East Asians, ~2-4% in Africans.
Reactive Arthritis Susceptibility moderate risk: HLA-B27 carriers have increased susceptibility to reactive arthritis following certain infections (Chlamydia, Salmonella, Shigella, Yersinia).
Evidence: OR ~10-20 · Source: Rheumatology literature; Brewerton et al. 1973
Anterior Uveitis Susceptibility moderate risk: HLA-B27 is associated with acute anterior uveitis. If experiencing sudden eye pain, redness, or light sensitivity, seek ophthalmologic evaluation promptly.
Evidence: OR ~10-15 · Source: Ophthalmology literature

How is HLA-B*27 inferred from a consumer DNA file?

Consumer chips do not sequence HLA genes. HLA-B*27 is inferred from the tag SNP rs4349859 (risk allele A), which travels with the HLA allele on the same stretch of chromosome. How reliably it does so (r²) differs by ancestry:

European	0.9
East Asian	0.85
African	0.8
Global	0.85

A tag-SNP call is a probability, not a laboratory HLA type. A positive result that would change a prescription should be confirmed by clinical HLA typing.

See whether your DNA file carries the HLA-B*27 tag
Upload your 23andMe, AncestryDNA or WeGene raw file → · Ask G2: “Am I likely to carry HLA-B*27, and what should I tell my doctor?”

Genetic associations describe risk across populations, not a diagnosis for any one person. Most variants shift risk modestly and act alongside lifestyle, environment and other genes. Consumer DNA chips do not read every position and can be wrong at any single one. For general education only; talk to a clinician or genetic counsellor before acting on anything here, and never change a prescribed medicine without your prescriber.