What you carry at this position in your DNA and what research says about it.
Macular Degeneration Protection: 8/10 evidence, 31 publications.
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Sample genotype (not yours): G/G
Typical Macular Degeneration Risk
Two copies of the common G allele mean complement system activity and macular degeneration risk are at typical baseline levels.
What this genotype means: Standard complement system activation; Baseline risk of age-related macular degeneration.
Sample genotype (not yours): A/A
Significantly Lower Macular Degeneration Risk
Two copies of the protective A allele provide strong protection against age-related macular degeneration.
What this genotype means: Dampened complement pathway activation; Up to 70% lower risk of macular degeneration.
Sample genotype (not yours): G/A
Lower Macular Degeneration Risk
Carrying one copy of the protective A allele reduces the risk of developing age-related macular degeneration by about half.
What this genotype means: Slightly dampened complement pathway activation; Approximately 50% lower risk of macular degeneration.
Gene function and biological role
Gene Function: The CFB gene encodes complement factor B, a key component of the alternative pathway of the complement system [1]. This system is a crucial part of the innate immune response, helping the body clear pathogens and damaged cells. However, overactivation of this pathway can lead to chronic inflammation and tissue damage, particularly in the retina [1]. Complement factor B works alongside other proteins to amplify immune activation. Genetic variations in this gene can alter the stability and activity of the complement system, directly influencing susceptibility to inflammatory and degenerative diseases [1].
Variant Impact: The rs641153 variant represents a missense mutation in the CFB gene that changes the amino acid at position 32 from arginine to glutamine, known as p.Arg32Gln [1]. This specific structural change occurs in the Ba domain of the complement factor B protein [1]. The glutamine-encoding A allele produces a protein that binds less efficiently to its activation partners [1]. As a result, individuals carrying this variant experience dampened complement system activation [1]. This reduction in activity helps protect delicate tissues, such as the macula in the eye, from chronic inflammatory damage [2].
Key Insight: The protective A allele of this variant reduces the complement system's amplification efficiency, which acts like a natural shield against age-related macular degeneration.
Location: CFB. Chromosome 6 · 6p21.33 · 31.9 Mb
Estimated prevalence by population
Global 78.4%; European 82.8%; African 65.5%; East Asian 87.9%; South Asian 75.2%; Americas 81.0%; Ashkenazi 88.8%; Finnish 88.8%; Middle Eastern 81.9%; Amish 91.0%.
Estimated GG genotype frequency.
Global 20.0%; European 16.4%; African 30.9%; East Asian 11.7%; South Asian 23.1%; Americas 18.0%; Ashkenazi 10.8%; Finnish 10.9%; Middle Eastern 17.2%; Amish 8.8%.
Estimated GA genotype frequency.
Global 1.6%; European 0.8%; African 3.6%; East Asian 0.4%; South Asian 1.8%; Americas 1.0%; Ashkenazi 0.3%; Finnish 0.3%; Middle Eastern 0.9%; Amish 0.2%.
Estimated AA genotype frequency.
Showing effects for G/G genotype
Organ Systems
Vision & Eye Health
Macular Degeneration. Evidence: 8/10. Source: PMID 24392338. Typical Risk.
Dry Macular Degeneration. Evidence: 8/10. Source: PMID 22705344. Typical Risk.
Wet Macular Degeneration. Evidence: 8/10. Source: PMID 22705344. Typical Risk.
Immunity & Inflammation
Inflammatory & Circulating Protein Markers
Complement Activation. Evidence: 8/10. Source: PMID 21541267. Typical Activity.
Showing effects for A/A genotype
Macular Degeneration. Evidence: 8/10. Source: PMID 24392338. ~70% Lower Risk.
Dry Macular Degeneration. Evidence: 8/10. Source: PMID 22705344. Lower Risk.
Wet Macular Degeneration. Evidence: 8/10. Source: PMID 22705344. Lower Risk.
Complement Activation. Evidence: 8/10. Source: PMID 21541267. Reduced Activity.
Showing effects for G/A genotype
Macular Degeneration. Evidence: 8/10. Source: PMID 24392338. ~50% Lower Risk.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Having the G/G genotype means carrying two copies of the reference arginine allele at position 32 of the complement factor B protein [1]. This genotype represents the standard baseline for the general population, with typical levels of complement system activation [1]. Because there is no protective glutamine variant present, there is no inherited reduction in the risk of age-related macular degeneration [2]. The complement system will function at its normal capacity, which is essential for fighting infections but can contribute to age-related tissue wear in the retina over time [1]. Maintaining standard eye health practices, such as avoiding smoking and protecting eyes from UV light, remains important [2].
Standard complement system activation; Baseline risk of age-related macular degeneration.
Sample genotype: AA (Homozygous)
Carrying two copies of the A allele means all complement factor B proteins produced have the glutamine variation [1]. This uniform change significantly dampens the alternative complement pathway's amplification loop [1]. While the immune system remains fully capable of defending the body, the reduction in chronic, low-grade inflammation provides robust protection for the delicate tissues of the macula [2]. Clinical studies and meta-analyses indicate that individuals with the A/A genotype have up to a 70% lower risk of developing advanced age-related macular degeneration [3]. This makes the genotype one of the most significant genetic protective factors identified for preserving late-life vision [3].
Dampened complement pathway activation; Up to 70% lower risk of macular degeneration.
Sample genotype: GA (Heterozygous)
Carrying one copy of the A allele means producing a mix of standard and modified complement factor B proteins [1]. The modified protein, containing glutamine instead of arginine, is less efficient at driving the complement cascade [1]. This slight dampening of the immune response acts as a protective shield for the retina, reducing the likelihood of chronic inflammatory damage [2]. Large-scale genetic analyses show that individuals with this genotype have approximately a 50% lower risk of developing both dry and wet forms of macular degeneration compared to those with the G/G genotype [3]. This genetic protection is particularly valuable as macular degeneration is a leading cause of vision loss in older adults [3].
Slightly dampened complement pathway activation; Approximately 50% lower risk of macular degeneration.
Variants with shared genetic architecture
rs4151667 · CFB Gene · Chr 6 · Macular Degeneration Risk
rs1048709 · CFB Gene · Chr 6 · Eye Inflammation Risk
rs12614 · CFB Gene · Chr 6 · Hepatitis B and Eye Health
Complement factor B polymorphism 32W protects against age-related macular degeneration.
Content updated August 2026.
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