What you carry at this position in your DNA and what research says about it.
Psoriasis and Biologic Response: 6/10 evidence, 7 publications.
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Sample genotype (not yours): C/C
Higher Psoriasis Risk and Typical Biologic Response
This genotype is associated with a moderately increased risk of developing psoriasis and psoriatic arthritis. It also correlates with a standard or typical response to certain biologic therapies.
What this genotype means: ~1.28x higher risk of psoriasis; Increased susceptibility to psoriatic arthritis; Standard response to biologic therapies.
Sample genotype (not yours): C/T
Lower Psoriasis Risk and Better Biologic Response
This genotype is linked to a reduced risk of developing psoriasis and psoriatic arthritis. If the condition does develop, it is associated with a significantly better response to biologic treatments.
What this genotype means: ~21% lower risk of psoriasis; Reduced risk of psoriatic arthritis; Improved early response to biologic treatments.
Sample genotype (not yours): T/T
This genotype is associated with a reduced risk of psoriasis and psoriatic arthritis. It also correlates with a more favorable response to targeted biologic therapies.
Gene function and biological role
Gene Function: The IL12B gene encodes the p40 subunit shared by two critical inflammatory cytokines, interleukin-12 (IL-12) and interleukin-23 (IL-23) [1]. These cytokines play a central role in the differentiation of naive T-cells into Th1 and Th17 cells, which drive chronic inflammatory pathways [1]. Dysregulation of this signaling axis is a major contributor to the development of autoimmune skin conditions [2]. Because of its key role in orchestrating inflammation, the IL-12/IL-23 pathway is a primary target for modern biologic therapies [3].
Variant Impact: This variant, rs3213094, is an intron variant located within the IL12B gene that influences the expression of the inflammatory p40 subunit [4]. By altering cytokine levels, the variant modulates susceptibility to chronic plaque psoriasis and psoriatic arthritis [1]. It also serves as a significant pharmacogenomic marker, predicting how effectively a patient will respond to targeted biologic therapies [3]. The genetic variation at this locus helps explain why some individuals experience more intense early-stage inflammation or better treatment outcomes [3].
Key Insight: The same genetic variant that lowers your risk of developing psoriasis also makes you significantly more responsive to advanced biologic treatments if you do develop it.
Location: IL12B. Chromosome 5 · 5q33.3 · 159.3 Mb
Estimated prevalence by population
Global 54.6%; European 63.9%; African 43.6%; East Asian 27.6%; South Asian 40.7%; Americas 44.4%; Ashkenazi 69.4%; Finnish 67.3%; Middle Eastern 51.5%; Amish 64.5%.
Estimated CC genotype frequency.
Global 37.7%; European 32.1%; African 44.9%; East Asian 49.9%; South Asian 46.2%; Americas 44.5%; Ashkenazi 27.8%; Finnish 29.4%; Middle Eastern 40.5%; Amish 31.6%.
Estimated CT genotype frequency.
Global 7.7%; European 4.0%; African 11.6%; East Asian 22.5%; South Asian 13.1%; Americas 11.1%; Ashkenazi 2.8%; Finnish 3.2%; Middle Eastern 8.0%; Amish 3.9%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Organ Systems
Skin & Hair Conditions
Psoriasis. Evidence: 6/10. Source: PMID 19169255. ~1.28x Risk.
Pharmacogenomics
Immunosuppressant & Biologic Response
Ustekinumab Response. Evidence: 5/10. Source: PMID 27564082. Typical Response.
Immunity & Inflammation
Autoimmune Diseases
Psoriatic Arthritis. Evidence: 3/10. Source: PMID 20606885. Increased Risk.
Inflammatory & Circulating Protein Markers
Cytokine Regulation. Evidence: 3/10. Source: PMID 21463712. Typical Levels.
Showing effects for C/T genotype
Psoriasis. Evidence: 6/10. Source: PMID 19169255. ~0.79x Risk.
Ustekinumab Response. Evidence: 5/10. Source: PMID 27564082. Stronger Response.
Psoriatic Arthritis. Evidence: 3/10. Source: PMID 20606885. Lower Risk.
Cytokine Regulation. Evidence: 3/10. Source: PMID 21463712. Altered Levels.
Showing effects for T/T genotype
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Carrying two copies of the C allele is associated with a higher susceptibility to chronic plaque psoriasis [1]. This genetic profile is linked to an approximate 1.28-fold increase in the odds of developing the condition compared to carriers of the T allele [2]. The increased risk extends to psoriatic arthritis, a related inflammatory joint condition [3]. Furthermore, individuals with this genotype tend to show a standard or less rapid early response to biologic treatments such as ustekinumab [4]. This is because the underlying genetic structure maintains a baseline level of cytokine-driven inflammation that may require more intensive management [4]. Understanding this genetic baseline can help clinicians tailor treatment strategies more effectively from the start.
~1.28x higher risk of psoriasis; Increased susceptibility to psoriatic arthritis; Standard response to biologic therapies.
Sample genotype: CT (Heterozygous)
Carrying one copy of the protective T allele is associated with a lower risk of developing psoriasis [1]. Research indicates that this genotype reduces the odds of psoriasis by approximately 21% compared to the typical baseline [2]. The protective effect also extends to related chronic inflammatory joint issues [3]. If treatment for moderate-to-severe psoriasis is ever required, individuals with this genotype tend to respond exceptionally well to biologic therapies like ustekinumab [4]. This enhanced response is particularly evident in the early stages of treatment, leading to faster skin clearance [4]. The genetic variation likely modulates the IL-12/IL-23 pathway to make it more sensitive to therapeutic blockade [4].
~21% lower risk of psoriasis; Reduced risk of psoriatic arthritis; Improved early response to biologic treatments.
Sample genotype: TT (Homozygous)
Carrying two copies of the protective T allele provides significant protection against the development of psoriasis [1]. This genetic profile is associated with a 21% reduction in the odds of developing chronic plaque psoriasis [2]. The protective benefit is also observed for psoriatic arthritis, helping to shield the joints from autoimmune inflammation [3]. In the event that inflammatory symptoms do occur, this genotype is linked to a highly favorable response to biologic drugs targeting the IL-12/IL-23 pathway [4]. Patients carrying the T allele often experience more rapid and pronounced skin clearance during the initial weeks of therapy [4]. This is due to a more favorable baseline regulation of inflammatory cytokines [5].
Variants with shared genetic architecture
rs12188300 · IL12B Gene · Chr 5 · Psoriasis Risk
rs2546890 · IL12B Gene · Chr 5 · Autoimmune Disease Risk
rs10045431 · IL12B Gene · Chr 5 · Inflammatory Bowel Disease Risk
Genetics of psoriasis and psoriatic arthritis.
Candidate gene polymorphisms and risk of psoriasis: A pilot study.
Content updated August 2026.
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