CRTH2 rs538399: Understanding Your Genetic Variant
The rs538399 variant is a single-nucleotide change located within the PTGDR2 gene, which encodes the CRTH2 receptor. This receptor plays a key role in immune cell activation, and the variant has been studied for its potential associations with allergic rhinitis and inflammatory responses.
What each genotype means
Typical receptor activity
This genotype represents the common form of the PTGDR2 gene variant. Research into this specific site is limited, and current evidence does not suggest a significant deviation from typical prostaglandin D2 receptor function or allergic response patterns.
This is the most common genotype observed in most global populations.
Potential altered receptor sensitivity
Carrying one copy of the T allele may be associated with subtle differences in how your immune cells respond to prostaglandin D2, a molecule involved in allergic inflammation. Because the evidence for this specific variant is limited, it is unclear how this influences your personal risk for conditions like allergic rhinitis or asthma.
Carried by a significant portion of the population, with a minor allele frequency typically ranging between 8% and 15% in European and East Asian groups.
Possible increased receptor sensitivity
This genotype involves two copies of the T allele, which some research suggests may be linked to variations in eosinophil activation or allergic rhinitis severity. As the evidence remains limited and mixed, this finding should not be used to predict health outcomes; please discuss any concerns regarding allergic symptoms with your healthcare provider.
This is the least common genotype, occurring at a frequency consistent with the reported minor allele frequency of 8% to 15% in European and East Asian populations.
What is rs538399?
The rs538399 variant is a specific single-nucleotide polymorphism (SNP) located within the PTGDR2 gene, also known as the CRTH2 gene. A SNP represents a variation at a single position in the DNA sequence among individuals. This particular variant is situated in a region of the gene that may influence how the body regulates the production or stability of the CRTH2 receptor. In the context of human genetics, rs538399 is categorized as a trait-associated variant, meaning researchers have investigated whether carrying specific versions of this DNA sequence correlates with observable differences in health or immune function. Because it is located in a functional area of the gene, scientists have hypothesized that it could alter the biological activity of the receptor, though the exact mechanisms remain a subject of ongoing scientific inquiry.
The Role of the CRTH2 Gene
The PTGDR2 gene encodes the CRTH2 protein, which stands for Chemoattractant Receptor-homologous molecule expressed on Th2 cells. This protein functions as a receptor for prostaglandin D2, a lipid mediator involved in the body's inflammatory response. CRTH2 is primarily found on the surface of specific immune cells, including eosinophils, basophils, and Th2 lymphocytes. When prostaglandin D2 binds to this receptor, it triggers a signaling cascade that promotes the migration and activation of these cells to sites of inflammation. This process is a fundamental part of the body's defense mechanism, but it is also heavily implicated in allergic inflammation. By mediating the recruitment of these cells, the CRTH2 receptor helps coordinate the immune response that characterizes conditions like allergic rhinitis, asthma, and atopic dermatitis.
Research and Evidence Strength
The evidence linking rs538399 to specific health traits is currently considered limited. While some studies have explored the role of CRTH2 variants in allergic diseases, results have been inconsistent across different populations. For instance, while some research has suggested that variants in the 3'-UTR region of the CRTH2 gene might influence mRNA stability and asthma susceptibility, other studies—such as those conducted in Japanese populations—have failed to replicate these findings. This discrepancy highlights the complexity of genetic associations, where the impact of a single variant can be influenced by a person's broader genetic background, environmental factors, and ancestry. Because the findings are mixed and not universally replicated, it is important to view these associations as preliminary rather than definitive markers for disease risk or severity.
Population Frequency
The frequency of the rs538399 variant varies depending on ancestral background. Current data indicates a minor allele frequency (MAF) ranging from approximately 0.08 to 0.15 in both European and East Asian populations. This means that the variant is relatively common, appearing in a significant portion of these groups. However, frequency alone does not determine the clinical significance of a variant. Because the variant is present in a notable percentage of the population, researchers have had ample opportunity to study it, yet the lack of consistent, strong associations across diverse cohorts suggests that its individual impact on health is likely subtle or dependent on complex interactions with other genes and environmental triggers.
Interpreting Your Results
If you have information about your rs538399 genotype, it is important to understand that this information is for educational purposes only. Genetic variants like rs538399 are just one small piece of a much larger puzzle involving your overall health, lifestyle, and environment. You cannot use this information to diagnose a condition or predict your personal risk for allergic diseases. If you are concerned about symptoms related to allergies or inflammation, the most effective approach is to consult with a healthcare professional, such as an allergist or immunologist. They can provide a comprehensive evaluation based on your clinical history and physical examination. Never make changes to your medical care or medication regimen based on genetic data without first discussing it with your doctor or a qualified pharmacist.
How common is this variant?
The rs538399 variant has a minor allele frequency of approximately 0.08 to 0.15 in European and East Asian populations.
Frequently asked questions
Is rs538399 a cause of asthma?
No, rs538399 is not considered a direct cause of asthma. While some research has investigated its potential link to allergic conditions, the evidence is limited and inconsistent across different populations.
Can I use this variant to predict my allergy risk?
No, you cannot use this variant to predict your risk of developing allergies. Genetic associations for complex traits like allergies are influenced by many genes and environmental factors, and this variant does not have a strong, predictive clinical value.
What should I do if I have the 'risk' genotype?
If you are concerned about your health, you should focus on your symptoms rather than your genotype. Discuss any concerns about allergies or immune health with a qualified healthcare provider.
Does this variant affect how I respond to allergy medication?
There is no established evidence that rs538399 dictates how you respond to specific allergy medications. Always consult your doctor or pharmacist regarding any questions about your medication dosing or effectiveness.
Sources & further reading
Educational information only, last refreshed 10/17/2026. Not medical advice — these associations describe population statistics, not individual predictions.
Curious what your genotype is for rs538399?
Upload a raw DNA file from 23andMe, AncestryDNA, MyHeritage, or FamilyTreeDNA and see this variant — plus thousands more — interpreted in your full report.
Get my report — $29