What you carry at this position in your DNA and what research says about it.
Autoimmune Disease Risk: 9/10 evidence, 51 publications.
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Sample genotype (not yours): C/C
Lower Autoimmune Risk but Slightly Higher Bowel Inflammation Risk
Carrying two copies of the C allele is associated with a lower risk of several autoimmune conditions, including type 1 diabetes and psoriasis. However, this genotype is linked to a slightly higher risk of inflammatory bowel disease.
What this genotype means: Lower risk of type 1 diabetes; Lower risk of psoriasis; Slightly higher risk of inflammatory bowel disease.
Sample genotype (not yours): C/T
Moderately Increased Risk of Autoimmune Conditions
Carrying one copy of the T allele moderately increases the risk of developing autoimmune diseases such as type 1 diabetes and psoriasis. This is due to slightly elevated baseline immune activity.
What this genotype means: Moderately increased risk of type 1 diabetes; Moderately increased risk of psoriasis; Slightly lower risk of inflammatory bowel disease.
Sample genotype (not yours): T/T
Higher Risk of Autoimmune Conditions
Carrying two copies of the T allele is linked to a higher risk of autoimmune diseases like type 1 diabetes and psoriasis. This genotype causes constitutively active immune signaling.
What this genotype means: Higher risk of type 1 diabetes; Higher risk of psoriasis; Lower risk of inflammatory bowel disease.
Gene function and biological role
Gene Function: The IFIH1 gene encodes MDA5, a critical intracellular sensor that detects viral double-stranded RNA [1]. Upon detecting viral genetic material, MDA5 triggers a signaling cascade that produces type I interferons to fight off infections [1]. However, overactive signaling can lead to chronic inflammation and autoimmune diseases [2]. This gene is highly expressed in immune cells and pancreatic islets, making its regulation vital for immune balance [3].
Variant Impact: The rs1990760 variant is a missense mutation that changes the amino acid at position 946 from alanine to threonine (p.Ala946Thr) [2]. This change occurs in the regulatory domain of the MDA5 protein, altering its ATPase activity [4]. The T allele (threonine) is a gain-of-function variant that causes constitutively higher basal interferon signaling [4]. While this enhanced activity helps the body clear viral infections more effectively, it also increases susceptibility to autoimmune conditions [3].
Key Insight: The genetic variant that increases your risk for type 1 diabetes and psoriasis actually helps your body fight off viral infections more effectively.
Location: IFIH1. Chromosome 2 · 2q24.2 · 162.3 Mb
Origin Story: The T allele represents an evolutionary trade-off where enhanced antiviral defense against pathogens was selected for, despite raising the risk of autoimmune diseases.
Estimated prevalence by population
Global 33.5%; European 15.2%; African 66.4%; East Asian 64.7%; South Asian 23.5%; Americas 31.1%; Ashkenazi 29.0%; Finnish 18.7%; Middle Eastern 25.7%; Amish 18.2%.
Estimated CC genotype frequency.
Global 42.7%; European 47.6%; African 30.2%; East Asian 31.4%; South Asian 50.0%; Americas 49.3%; Ashkenazi 49.7%; Finnish 49.1%; Middle Eastern 50.0%; Amish 48.9%.
Estimated CT genotype frequency.
Global 23.8%; European 37.1%; African 3.4%; East Asian 3.8%; South Asian 26.6%; Americas 19.6%; Ashkenazi 21.3%; Finnish 32.3%; Middle Eastern 24.3%; Amish 32.9%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Organ Systems
Skin & Hair Conditions
Psoriasis. Evidence: 9/10. Source: PMID 25903422. Typical Risk.
Cardiovascular & Metabolic
Diabetes & Glycemic Traits
Type 1 Diabetes. Evidence: 8/10. Source: PMID 17554260. Typical Risk.
Blood Cell & Iron Traits
White Blood Cell Count. Evidence: 8/10. Source: PMID 32888494. Slightly Higher.
Immunity & Inflammation
Chronic Inflammatory Diseases
Inflammatory Bowel Disease. Evidence: 7/10. Source: PMID 26192919. ~1.07x Risk.
Autoimmune Diseases
Lupus. Evidence: 7/10. Source: PMID 19838195. Typical Risk.
Thyroid Autoimmunity. Evidence: 8/10. Source: PMID 32581359. Typical Risk.
Showing effects for C/T genotype
Psoriasis. Evidence: 9/10. Source: PMID 25903422. ~1.18x Risk.
Type 1 Diabetes. Evidence: 8/10. Source: PMID 17554260. Increased Risk.
White Blood Cell Count. Evidence: 8/10. Source: PMID 32888494. Typical.
Inflammatory Bowel Disease. Evidence: 7/10. Source: PMID 26192919. Slightly Lower Risk.
Lupus. Evidence: 7/10. Source: PMID 19838195. Increased Risk.
Thyroid Autoimmunity. Evidence: 8/10. Source: PMID 32581359. Increased Risk.
Showing effects for T/T genotype
Psoriasis. Evidence: 9/10. Source: PMID 25903422. Increased Risk.
Type 1 Diabetes. Evidence: 8/10. Source: PMID 17554260. Highest Risk.
White Blood Cell Count. Evidence: 8/10. Source: PMID 32888494. Slightly Lower.
Inflammatory Bowel Disease. Evidence: 7/10. Source: PMID 26192919. Lowest Risk.
Lupus. Evidence: 7/10. Source: PMID 19838195. Highest Risk.
Thyroid Autoimmunity. Evidence: 8/10. Source: PMID 32581359. Highest Risk.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Having the C/C genotype means you carry two copies of the reference alanine allele at position 946 of the IFIH1 protein. This version of the protein maintains typical, baseline interferon signaling, which does not overstimulate the immune system [1]. Consequently, large-scale genetic studies show a significantly lower risk of developing type 1 diabetes [2] and psoriasis [3] compared to carriers of the T allele. It is also associated with a lower risk of systemic lupus erythematosus [4] and autoimmune thyroid disease [5]. However, there is a minor trade-off, as the C allele is linked to a slightly increased risk of inflammatory bowel disease [6]. Overall, this genotype represents a more balanced immune response with lower susceptibility to most major autoimmune conditions.
Lower risk of type 1 diabetes; Lower risk of psoriasis; Slightly higher risk of inflammatory bowel disease.
Sample genotype: CT (Heterozygous)
Carrying the C/T genotype means you have one copy of the threonine variant, which causes a moderate gain of function in the MDA5 viral sensor. This variant leads to slightly elevated baseline production of type I interferons, keeping the immune system on a higher state of alert [1]. This hyper-responsiveness increases the risk of several autoimmune disorders, including type 1 diabetes [2] and psoriasis [3]. It is also associated with an increased susceptibility to systemic lupus erythematosus [4] and autoimmune thyroid disease [5]. On the positive side, this genotype is associated with a slightly lower risk of inflammatory bowel disease [6]. The moderate increase in interferon activity may also provide slightly better protection against certain viral infections.
Moderately increased risk of type 1 diabetes; Moderately increased risk of psoriasis; Slightly lower risk of inflammatory bowel disease.
Sample genotype: TT (Homozygous)
Having the T/T genotype means you carry two copies of the threonine variant, resulting in a constitutively active MDA5 protein [1]. This gain-of-function variant causes a persistent, elevated baseline level of type I interferon signaling, which can cause the immune system to mistakenly attack healthy tissues [1]. Large genetic studies have consistently linked this genotype to a significantly higher risk of type 1 diabetes [2] and psoriasis [3]. It also increases the risk of other autoimmune conditions, such as systemic lupus erythematosus [4] and autoimmune thyroid disease [5]. Conversely, this genotype is associated with a lower risk of inflammatory bowel disease [6]. While the overactive immune response increases autoimmune risk, it may historically have provided an evolutionary advantage by protecting against severe viral infections.
Higher risk of type 1 diabetes; Higher risk of psoriasis; Lower risk of inflammatory bowel disease.
Variants with shared genetic architecture
rs2111485 · IFIH1 Gene · Chr 2 · Autoimmune Disease Risk
rs3747517 · IFIH1 Gene · Chr 2 · Autoimmune Disease Risk
rs35667974 · IFIH1 Gene · Chr 2 · Autoimmune Disease Risk
Cumulative effect of IFIH1 variants and increased gene expression associated with type 1 diabetes.
Robust associations of four new chromosome regions from genome-wide analyses of type 1 diabetes.
FLT3 stop mutation increases FLT3 ligand level and risk of autoimmune thyroid disease.
Content updated August 2026.
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