CFHR3 rs6677604: What Your Genotype Means
The rs6677604 variant is a single nucleotide polymorphism located within the CFH gene region. It is primarily studied as a genetic tag for a structural deletion of the CFHR3 and CFHR1 genes, which has been associated with a reduced risk of age-related macular degeneration.
What each genotype means
Typical complement regulation
This genotype represents the common, non-deletion state at this locus. Research indicates that individuals with this genotype do not carry the protective deletion of the CFHR3 and CFHR1 genes associated with this variant, meaning they do not receive the specific protective effect against age-related macular degeneration linked to that deletion.
This is the most common genotype in European populations, where the minor allele (A) has a frequency of approximately 0.20.
Heterozygous for deletion-tagging variant
You carry one copy of the allele that tags the CFHR3-CFHR1 deletion. Because this variant is a marker for a structural deletion, carrying one copy suggests you may have a partial reduction in the expression of these complement-related proteins, which has been studied for its complex role in immune-mediated conditions and eye health.
Carried by a significant portion of the population, reflecting the roughly 20-30% frequency of the deletion-associated haplotype in Western populations.
Associated with protective deletion
This genotype is a strong marker for the homozygous deletion of the CFHR3 and CFHR1 genes. Research has associated this deletion with a protective effect against age-related macular degeneration, though it has also been linked to an increased risk of certain kidney conditions like atypical hemolytic uremic syndrome in some studies. Please discuss any health concerns or family history with your clinician.
This genotype is found in approximately 4-9% of individuals of European ancestry, with higher frequencies observed in some other populations.
Understanding the rs6677604 Variant
The rs6677604 variant is a specific position in the human genome located within intron 11 of the Complement Factor H (CFH) gene. In genetic research, this SNP is frequently used as a proxy or 'tag' for a larger structural variation known as the CFHR3-CFHR1 deletion. Because this deletion involves the physical removal of segments of DNA containing the CFHR3 and CFHR1 genes, it is difficult to measure directly using standard genotyping arrays. Instead, researchers look at the rs6677604 variant to infer the presence or absence of these genes. When an individual carries the 'A' allele at this position, it is strongly correlated with the deletion of the CFHR3-CFHR1 locus. This makes rs6677604 a critical tool for scientists investigating how variations in the complement system—a part of the immune system—influence health outcomes.
The Role of CFHR3 and CFHR1
The CFHR3 and CFHR1 genes belong to the complement factor H-related protein family. These proteins are involved in regulating the complement system, a complex network of proteins that helps the body clear pathogens and damaged cells. The complement system must be tightly controlled to prevent it from attacking the body's own healthy tissues. Research suggests that CFHR3 and CFHR1 proteins may compete with Complement Factor H (CFH), a major regulator that prevents excessive inflammation. By deleting these genes, the balance of the complement system is altered. While this deletion is linked to a lower risk of age-related macular degeneration (AMD), it has also been studied in the context of other conditions, such as atypical hemolytic uremic syndrome (aHUS), where the loss of these proteins might increase susceptibility to certain immune-related complications.
Research Associations and Evidence
The association between the CFHR3-CFHR1 deletion (tagged by rs6677604) and age-related macular degeneration is one of the most well-documented findings in ocular genetics. Multiple large-scale studies have observed that individuals carrying the deletion have a lower risk of developing advanced AMD. However, the evidence is considered complex because this region of the genome is highly interconnected. Some researchers have noted that the protective effect might be influenced by other nearby genetic variations, such as the well-known Y402H variant in the CFH gene. Furthermore, while the association with AMD is statistically significant, the clinical impact for any single individual is not absolute. Genetic factors are only one piece of the puzzle, and environmental factors, such as smoking and diet, play substantial roles in the development of macular health issues.
Population Frequency and Distribution
The frequency of the rs6677604 variant and the associated CFHR3-CFHR1 deletion varies significantly across different ancestral populations. In European populations, the minor allele frequency for the 'A' allele is approximately 0.20, meaning the deletion is relatively common. Research indicates that this deletion is even more frequent in African populations, where it may reach frequencies as high as 40%. This variation in frequency is a subject of ongoing study, as it may help explain differences in the prevalence of AMD across diverse groups. Because the deletion is so common in some populations, it is considered a normal variation rather than a rare mutation. Understanding these frequency differences is essential for researchers to accurately interpret how genetic risk factors for complex diseases manifest across different global ancestries.
Interpreting Your Genetic Information
If you have received information about your rs6677604 genotype, it is important to understand that this is a statistical association, not a medical diagnosis. The presence of a specific genotype does not guarantee that you will or will not develop a particular condition. Genetic markers like rs6677604 provide insights into biological predispositions, but they do not account for the full spectrum of health, including lifestyle, environment, and other genetic factors. You cannot use this information to self-diagnose or make medical decisions. If you are concerned about your risk for age-related macular degeneration or other conditions, the most appropriate step is to consult with an eye care professional or a genetic counselor. They can provide context based on your personal and family medical history, which is far more predictive than any single genetic variant.
How common is this variant?
The rs6677604 'A' allele, which tags the CFHR3-CFHR1 deletion, has a minor allele frequency of approximately 0.20 in European populations and is found at higher frequencies in African populations.
Frequently asked questions
Does having the rs6677604 A/A genotype mean I will never get AMD?
No. While the A/A genotype is associated with a lower risk of age-related macular degeneration, it does not provide immunity. Many factors, including age, smoking, and other genetic variants, contribute to the development of the condition.
Is the CFHR3-CFHR1 deletion harmful?
The deletion is associated with both potential benefits and risks. While it is linked to a lower risk of AMD, it has also been studied for its potential association with an increased risk of other immune-related conditions like atypical hemolytic uremic syndrome.
Can I change my risk if I have this variant?
You cannot change your genotype, but you can manage your health through lifestyle choices. For eye health, this includes regular screenings with an eye doctor, maintaining a healthy diet, and avoiding smoking, which are known to impact AMD risk.
Why do researchers use rs6677604 to study a deletion?
The rs6677604 variant is located in a region that is physically linked to the CFHR3-CFHR1 genes. Because it is easier to detect this single SNP than to map the entire structural deletion, it serves as a reliable genetic marker for the presence or absence of those genes.
Sources & further reading
Educational information only, last refreshed 9/16/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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