What you carry at this position in your DNA and what research says about it.
Heart Disease Risk: 7/10 evidence, 27 publications.
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Sample genotype (not yours): A/A
Variable Heart Risk and Altered Drug Response
Conflicting cardiovascular risk reports characterize this genetic profile, with effects that may vary by ethnic background.
What this genotype means: Conflicting cardiovascular risk depending on ancestry; Increased risk of heart damage from doxorubicin chemotherapy; Altered response to certain cancer treatments.
Sample genotype (not yours): A/G
Typical Heart Risk with Moderate Chemotherapy Sensitivity
Baseline risk for cardiovascular issues remains typical with this genetic profile.
What this genotype means: Typical baseline cardiovascular risk; Slightly increased risk of heart damage from doxorubicin chemotherapy.
Sample genotype (not yours): G/G
Typical Heart Risk and Standard Drug Response
Standard cardiovascular health and typical responses to chemotherapy treatments characterize this profile.
What this genotype means: Typical baseline cardiovascular risk; Standard risk of side effects from chemotherapy.
Gene function and biological role
Gene Function: The CYBA gene encodes the p22phox subunit of cytochrome b-245, which is a critical component of the NADPH oxidase enzyme complex [1]. This enzyme complex is a major source of reactive oxygen species in vascular cells and phagocytes [2]. By generating superoxide, NADPH oxidase plays a central role in vascular signaling, inflammation, and host defense [1]. Variations in this gene can alter enzyme activity, thereby influencing oxidative stress levels in the cardiovascular system [2].
Variant Impact: A missense mutation in exon 4 of the CYBA gene defines the rs4673 variant, commonly known as C242T or Tyr72His [3]. This genetic variation results in the substitution of histidine for tyrosine at position 72 of the p22phox protein [3]. This specific change is located in a heme-binding region, which can impair the stability and function of the NADPH oxidase complex [4]. Consequently, this variant has been shown to reduce the generation of reactive oxygen species in human blood vessels and immune cells [5].
Key Insight: This variant can reduce the body's production of cellular free radicals, which has a complex, double-edged effect on cardiovascular health depending on your ancestry.
Location: CYBA. Chromosome 16 · 16q24.2 · 88.6 Mb
Estimated prevalence by population
Global 12.9%; European 11.4%; African 20.9%; East Asian 0.8%; South Asian 12.8%; Americas 7.7%; Ashkenazi 17.7%; Finnish 3.1%; Middle Eastern 20.5%; Amish 9.6%.
Estimated AA genotype frequency.
Global 43.7%; European 44.7%; African 49.6%; East Asian 16.3%; South Asian 45.9%; Americas 40.1%; Ashkenazi 48.8%; Finnish 29.1%; Middle Eastern 49.5%; Amish 42.8%.
Estimated AG genotype frequency.
Global 43.4%; European 43.9%; African 29.5%; East Asian 82.8%; South Asian 41.3%; Americas 52.2%; Ashkenazi 33.5%; Finnish 67.8%; Middle Eastern 30.0%; Amish 47.6%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Cardiovascular & Metabolic
Heart Disease
Heart Disease. Evidence: 7/10. Source: PMID 10440830. Conflicting Risk.
Hypertension
Blood Pressure. Evidence: 7/10. Source: PMID 34989438. Associated.
Pharmacogenomics
Chemotherapy Response
Chemotherapy Toxicity. Evidence: 5/10. Source: PMID 16330681. Increased Risk.
Cancer & Oncology
Cancer Prognosis & Treatment Outcome
Lymphoma Treatment Outcome. Evidence: 5/10. Source: PMID 19448608. Decreased Survival.
Immunity & Inflammation
Chronic Inflammatory Diseases
Inflammatory Bowel Disease. Evidence: 7/10. Source: PMID 30709874. No Increased Risk.
Lifestyle, Fitness & Aging
Height & Body Size
Height. Evidence: 8/10. Source: PMID 36224396. Slightly Taller.
Showing effects for A/G genotype
Heart Disease. Evidence: 7/10. Source: PMID 10440830. Typical Risk.
Lymphoma Treatment Outcome. Evidence: 5/10. Source: PMID 19448608. Typical Survival.
Showing effects for G/G genotype
Chemotherapy Toxicity. Evidence: 5/10. Source: PMID 16330681. Typical Risk.
Height. Evidence: 8/10. Source: PMID 36224396. Typical Height.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Two copies of the A allele correspond to the variant often referred to as 242T in medical literature. Some clinical studies suggest this genotype reduces oxidative stress and lowers the risk of coronary artery disease, particularly in Asian populations [1]. However, other research, including studies in European cohorts, has found no protective effect or even an increased risk of vascular complications [2]. Additionally, if undergoing chemotherapy with anthracyclines like doxorubicin, this genotype is linked to a higher risk of drug-induced heart damage [3]. It has also been associated with lower survival rates in patients receiving R-CHOP therapy for lymphoma [4].
Conflicting cardiovascular risk depending on ancestry; Increased risk of heart damage from doxorubicin chemotherapy; Altered response to certain cancer treatments.
Sample genotype: AG (Heterozygous)
One copy of each allele represents a common intermediate state. Your baseline risk for coronary artery disease and high blood pressure is considered typical, as most studies show no major deviation from the general population [1]. However, in the context of cancer treatment, having this genotype is still associated with an elevated risk of heart damage when taking the chemotherapy drug doxorubicin [2]. On the other hand, some studies suggest a decreased risk of other side effects like anemia or mucositis during certain chemotherapy regimens [3]. Overall, this genetic profile has a minimal impact on everyday health unless specific medical treatments are required.
Typical baseline cardiovascular risk; Slightly increased risk of heart damage from doxorubicin chemotherapy.
Sample genotype: GG (Homozygous)
Two copies of the G allele, which corresponds to the 242C reference genotype in scientific literature, represent the most common genetic profile [1]. This genotype is associated with standard levels of NADPH oxidase activity and typical baseline oxidative stress [2]. Clinical studies generally show a typical risk for coronary artery disease, stroke, and hypertension [3]. Unlike carriers of the A allele, you do not have an elevated risk of heart damage when treated with doxorubicin chemotherapy [4]. Your response to standard cancer therapies and overall survival rates are typical [5].
Typical baseline cardiovascular risk; Standard risk of side effects from chemotherapy.
Variants with shared genetic architecture
rs17608766 · GOSR2 Gene · Chr 17 · Blood Pressure
rs55730499 · LPA Gene · Chr 6 · Heart Disease Risk
rs5880 · CETP Gene · Chr 16 · HDL Cholesterol Levels
NADPH oxidase CYBA polymorphisms, oxidative stress and cardiovascular diseases.
Association of p22phox gene C242T polymorphism with coronary artery disease: a meta-analysis.
Content updated August 2026.
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