CRB1 rs61748240: Understanding This Rare Retinal Variant
The rs61748240 variant is a rare genetic change located within the CRB1 gene, which is essential for eye development. It has been studied for its potential association with severe, early-childhood onset retinal dystrophies and Leber congenital amaurosis.
What each genotype means
Typical retinal risk profile
You carry two copies of the standard G allele for this variant in the CRB1 gene. This genotype is not associated with an increased genetic risk for CRB1-related inherited retinal degenerations such as Leber congenital amaurosis. Your risk for these specific conditions remains in line with typical baseline population rates.
Carried by more than 99.8% of individuals across all major continental populations.
Carrier of rare retinal variant
You have one copy of the rare T allele (corresponding to c.1841G>T, p.Gly614Val), which has been implicated in autosomal recessive retinal conditions such as early-onset severe retinal dystrophy and Leber congenital amaurosis. Because CRB1-associated retinopathies are inherited in an autosomal recessive manner, carrying a single altered copy is generally not expected to cause symptoms on its own. Clinical manifestations typically occur only when a second pathogenic mutation is inherited on the other CRB1 gene copy.
Carried by fewer than 1 in 1,000 individuals in the global population (minor allele frequency < 0.001 in gnomAD).
High risk for early-onset retinal dystrophy
You carry two copies of the rare T allele, a missense variant categorized as pathogenic or likely pathogenic in the literature for autosomal recessive CRB1-related retinopathies. Published research associates biallelic changes at this locus with severe, early-childhood-onset visual impairment, including Leber congenital amaurosis and retinitis pigmentosa. Given the severity of CRB1-associated conditions, clinical genetic counseling and comprehensive ophthalmic assessment are recommended to evaluate individual visual health.
Extremely rare; observed in far fewer than 1 in 1,000,000 individuals worldwide.
What is rs61748240?
The variant rs61748240 is a specific change in the DNA sequence of the CRB1 gene. In genetics, a single nucleotide polymorphism (SNP) like this represents a variation at a single position in the genome. This particular variant is classified as a missense mutation, meaning the change in the DNA code results in the production of a different amino acid during protein synthesis. Because the CRB1 gene provides instructions for making a protein that is critical for the structure and function of the retina, changes in this sequence can potentially disrupt normal biological processes. Researchers track these variants to understand how they might contribute to inherited conditions. It is important to note that the presence of a variant does not automatically result in a clinical condition, as many factors, including the inheritance pattern and the presence of other genetic modifiers, play a role in how a gene functions within the body.
The Role of the CRB1 Gene
The CRB1 gene, or Crumbs homolog 1, is primarily expressed in the retina, the light-sensitive tissue at the back of the eye. The protein it encodes is a key component of the cell-to-cell junctions in photoreceptor cells, which are the specialized cells that detect light. These junctions are vital for maintaining the structural integrity and polarity of the retina. When the CRB1 protein is dysfunctional, the retina may fail to develop or maintain its organized structure, leading to severe vision impairment. Research indicates that mutations in this gene are linked to a spectrum of inherited retinal dystrophies (IRDs), including Leber congenital amaurosis and early-onset severe retinal dystrophy. These conditions are characterized by the progressive loss of photoreceptor cells, which can lead to significant vision loss starting in childhood. Understanding the function of this gene is a major focus of current ophthalmological research, particularly in the development of potential gene therapies.
Research and Evidence Strength
The evidence linking rs61748240 to retinal disease is currently considered limited. While the CRB1 gene as a whole is well-established as a cause of various retinal dystrophies, the specific clinical impact of this individual variant requires further investigation. Scientific literature often categorizes variants based on their pathogenicity, and for many rare variants, the data is still accumulating. Current studies are focused on mapping the genotype-phenotype correlations, which help clinicians understand how specific genetic changes manifest as physical symptoms. Because this variant is rare, large-scale population studies are difficult to conduct, which contributes to the uncertainty regarding its exact effect size. Researchers are actively investigating how CRB1 mutations lead to retinal remodeling and inflammation, which may eventually provide more clarity on the role of specific variants like rs61748240. As with all genetic research, findings are subject to change as more data becomes available through clinical registries and genomic sequencing projects.
What You Can Do With This Information
If you have received information about this variant through genetic testing, it is important to approach the results with perspective. Genetic information is complex and should always be interpreted by a qualified healthcare professional, such as a genetic counselor or an ophthalmologist specializing in retinal diseases. You cannot use this information to self-diagnose or predict a specific health outcome. If you are concerned about your vision or a family history of retinal conditions, consult a medical professional who can provide a comprehensive clinical evaluation. They can help you understand the relevance of your genetic results in the context of your overall health and family history. Avoid making medical decisions based solely on online reports or raw data files. Instead, focus on maintaining regular eye exams and discussing any symptoms or concerns with your doctor, who can provide guidance based on the most current clinical standards and evidence-based practices.
How common is this variant?
The rs61748240 variant is a rare allele with a minor allele frequency (MAF) of less than 0.001 in the gnomAD database, meaning it is found in a very small fraction of the general population.
Frequently asked questions
Is rs61748240 a cause of blindness?
The CRB1 gene is associated with severe retinal dystrophies, but the specific impact of the rs61748240 variant is still being studied. Having a variant does not guarantee the development of a condition, and you should consult an eye specialist for a clinical assessment.
Where can I find more information on CRB1?
You can find reliable information on the CRB1 gene through resources like MedlinePlus Genetics or the National Center for Biotechnology Information (NCBI) Gene database. These platforms provide summaries of gene function and associated clinical conditions.
Are there treatments for CRB1-related conditions?
Research into gene therapies for CRB1-associated retinal dystrophies is ongoing, but there are currently no widely approved gene therapies specifically for this gene. Clinical trials are the primary way new treatments are being evaluated.
Should I be worried if I have this variant?
Genetic variants are common, and many have no impact on health. If you are concerned about your genetic results, the best step is to speak with a genetic counselor who can explain the findings in the context of your personal and family health history.
Sources & further reading
Educational information only, last refreshed 10/19/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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