What you carry at this position in your DNA and what research says about it.
Crohn's Disease Risk: 5/10 evidence, 23 publications.
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Sample genotype (not yours): G/G
Typical Crohn's and Arthritis Risk
Two copies of the G allele provide a standard baseline level of protection against chronic gut and joint inflammation. This genotype is associated with the lowest risk of developing Crohn's disease and ankylosing spondylitis.
What this genotype means: Typical baseline risk for Crohn's disease; Typical baseline risk for ankylosing spondylitis.
Sample genotype (not yours): A/A
Higher Crohn's and Arthritis Risk
Two copies of the A allele significantly increase susceptibility to inflammatory bowel disease and joint inflammation.
What this genotype means: ~2x increased risk of Crohn's disease; Increased risk of ankylosing spondylitis.
Sample genotype (not yours): G/A
Moderately Higher Crohn's and Arthritis Risk
Carrying one copy of the A allele moderately increases susceptibility to chronic inflammatory conditions of the gut and joints. Proactive lifestyle choices can help manage overall systemic inflammation.
What this genotype means: ~1.5x increased risk of Crohn's disease; Slightly increased risk of ankylosing spondylitis.
Gene function and biological role
Gene Function: The IL23R gene encodes a subunit of the receptor for interleukin-23, a pro-inflammatory cytokine that plays a pivotal role in the immune system. This receptor is highly expressed on T-cells, natural killer cells, and dendritic cells, where it helps coordinate the body's defense against pathogens [1]. When interleukin-23 binds to its receptor, it triggers a signaling cascade that promotes the survival and expansion of inflammatory Th17 cells [2]. Dysregulation of this pathway can lead to chronic, unchecked inflammation, particularly in the mucosal lining of the gut and in the joints [1] [2]. Consequently, genetic variations in this gene are heavily implicated in several autoimmune and chronic inflammatory disorders [2].
Variant Impact: The rs1004819 variant is an intronic change located within the IL23R gene on chromosome 1. Although it does not directly alter the amino acid sequence of the receptor protein, it is thought to influence gene expression or splicing patterns, thereby modulating the activity of the interleukin-23 pathway [1]. The minor A allele of this variant is strongly associated with an increased susceptibility to inflammatory bowel diseases and joint inflammation [2]. Conversely, the major G allele is associated with lower levels of inflammation and a reduced risk of autoimmune conditions [1] [2]. This variant serves as one of the most widely studied genetic markers for chronic inflammatory disorders [2].
Key Insight: The A allele of this variant significantly increases the risk of both Crohn's disease and ankylosing spondylitis, highlighting a shared genetic pathway between gut and joint inflammation.
Location: IL23R. Chromosome 1 · 1p31.3 · 67.2 Mb
Estimated prevalence by population
Global 48.3%; European 49.6%; African 49.5%; East Asian 18.2%; South Asian 18.8%; Americas 56.8%; Ashkenazi 43.3%; Finnish 54.3%; Middle Eastern 31.5%; Amish 44.7%.
Estimated GG genotype frequency.
Global 41.6%; European 41.7%; African 41.7%; East Asian 48.9%; South Asian 49.1%; Americas 37.1%; Ashkenazi 45.0%; Finnish 38.7%; Middle Eastern 49.3%; Amish 44.3%.
Estimated GA genotype frequency.
Global 10.1%; European 8.8%; African 8.8%; East Asian 32.9%; South Asian 32.0%; Americas 6.1%; Ashkenazi 11.7%; Finnish 6.9%; Middle Eastern 19.3%; Amish 11.0%.
Estimated AA genotype frequency.
Showing effects for G/G genotype
Immunity & Inflammation
Chronic Inflammatory Diseases
Crohn's Disease. Evidence: 5/10. Source: PMID 17804789. Typical Risk.
Ulcerative Colitis. Evidence: 4/10. Source: PMID 22735800. Typical Risk.
Autoimmune Diseases
Ankylosing Spondylitis. Evidence: 4/10. Source: PMID 22089529. Typical Risk.
Rheumatoid Arthritis. Evidence: 4/10. Source: PMID 23053963. Typical Risk.
Showing effects for A/A genotype
Crohn's Disease. Evidence: 5/10. Source: PMID 17804789. ~2x Higher Risk.
Ulcerative Colitis. Evidence: 4/10. Source: PMID 22735800. Increased Risk.
Ankylosing Spondylitis. Evidence: 4/10. Source: PMID 22089529. ~1.5x Higher Risk.
Rheumatoid Arthritis. Evidence: 4/10. Source: PMID 23053963. Increased Risk.
Showing effects for G/A genotype
Crohn's Disease. Evidence: 5/10. Source: PMID 17804789. ~1.5x Higher Risk.
Ulcerative Colitis. Evidence: 4/10. Source: PMID 22735800. Slightly Higher Risk.
Ankylosing Spondylitis. Evidence: 4/10. Source: PMID 22089529. ~1.2x Higher Risk.
Rheumatoid Arthritis. Evidence: 4/10. Source: PMID 23053963. Slightly Higher Risk.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Carrying two copies of the major G allele represents the baseline genetic profile for the IL23R gene. Large-scale genetic studies show that this genotype is associated with a typical, non-elevated risk for Crohn's disease and other inflammatory bowel disorders [1]. Because the G allele does not promote the overactivation of the interleukin-23 inflammatory pathway, joint health is also protected, resulting in a lower likelihood of developing ankylosing spondylitis compared to carriers of the A allele [2]. Individuals with this profile generally experience typical immune responses in the gut mucosa [1]. Maintaining a balanced diet rich in fiber and supporting a diverse gut microbiome can further reinforce this natural baseline protection [1] [2].
Typical baseline risk for Crohn's disease; Typical baseline risk for ankylosing spondylitis.
Sample genotype: AA (Homozygous)
Carrying two copies of the minor A allele represents the highest genetic risk profile for chronic inflammatory conditions at this locus. Research indicates that this genotype is associated with an approximate doubling of the risk for Crohn's disease [1]. Additionally, this profile is strongly linked to an increased risk of developing ankylosing spondylitis and other forms of inflammatory arthritis [2]. The double dose of the A allele is believed to lead to hyper-responsiveness in the interleukin-23 pathway, which can drive chronic inflammation in both the digestive tract and the skeletal system [1] [2]. Proactive monitoring for symptoms like persistent abdominal pain, chronic diarrhea, or lower back stiffness is highly advisable [1]. Engaging in regular low-impact exercise and working with healthcare professionals to maintain gut barrier integrity can be highly beneficial.
~2x increased risk of Crohn's disease; Increased risk of ankylosing spondylitis.
Sample genotype: GA (Heterozygous)
Possessing one copy of the minor A allele is associated with a moderate increase in the risk of developing Crohn's disease, with studies suggesting an odds ratio of approximately 1.5 compared to the baseline genotype [1]. This genetic variation is also linked to a slightly higher susceptibility to ankylosing spondylitis, a chronic inflammatory arthritis affecting the spine [2]. The presence of the A allele is thought to subtly enhance the activity of the interleukin-23 receptor pathway, leading to a more pronounced inflammatory response in mucosal tissues [1]. While this genotype increases susceptibility, it does not guarantee the development of any autoimmune condition [1] [2]. Managing stress, avoiding smoking, and focusing on an anti-inflammatory diet are practical ways to support long-term gut and joint health.
~1.5x increased risk of Crohn's disease; Slightly increased risk of ankylosing spondylitis.
Variants with shared genetic architecture
rs11209026 · IL23R Gene · Chr 1 · Autoimmune Disease Risk
rs7517847 · IL23R Gene · Chr 1 · Crohn Disease Risk
rs11465804 · IL23R Gene · Chr 1 · Inflammatory Disease Risk
Content updated August 2026.
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