TSC1 rs118203380: Tuberous Sclerosis Complex & Your Genotype
The rs118203380 variant is a rare genetic mutation located in the TSC1 gene. Clinical research classifies this specific single nucleotide polymorphism (SNP) as pathogenic, meaning it is strongly associated with the development of Tuberous Sclerosis Complex (TSC).
What each genotype means
Typical TSC1 genetic profile
This genotype represents the reference sequence for this region of the TSC1 gene. It is the standard genetic configuration found in the general population and is not associated with the pathogenic changes linked to Tuberous Sclerosis Complex.
This is the most common genotype observed across all global populations.
Pathogenic TSC1 variant
This genotype involves a specific deletion and insertion (often noted as a complex indel) that is classified as pathogenic. Research indicates this variant is associated with Tuberous Sclerosis Complex, a condition that can lead to the growth of noncancerous tumors in various organs. Please consult with a medical geneticist or your healthcare provider to discuss these findings in the context of your personal and family health history.
This specific genotype is extremely rare and is not typically found in general population databases.
Carrier of pathogenic variant
This genotype indicates that one copy of the TSC1 gene contains the pathogenic variant, while the other copy is the reference sequence. Because Tuberous Sclerosis Complex is typically inherited in an autosomal dominant manner, carrying one altered copy is clinically significant. You should discuss these results with a genetic counselor or physician to understand the implications for your health and potential screening needs.
This heterozygous genotype is rare and is generally identified only in clinical settings related to the diagnosis of Tuberous Sclerosis Complex.
What is rs118203380 and where is it located?
rs118203380 is a specific genetic variant, or single nucleotide polymorphism (SNP), located on chromosome 9 within the TSC1 gene. The TSC1 gene provides the body with instructions for producing a crucial protein called hamartin. In a typical cell, hamartin interacts closely with another protein called tuberin (produced by the TSC2 gene) to form a multi-protein complex. This complex acts as a tumor suppressor by negatively regulating the mTORC1 pathway, which is responsible for cell growth and proliferation. When a pathogenic variant like rs118203380 occurs, it can disrupt the normal structure or function of the hamartin protein. This disruption prevents the TSC1-TSC2 complex from effectively controlling cell growth, leading to the unchecked cellular proliferation characteristic of certain genetic conditions. Because this variant alters a fundamental mechanism of cellular regulation, it is closely monitored in clinical genetics.
Association with Tuberous Sclerosis Complex (TSC)
Clinical databases, including ClinVar, classify the rs118203380 variant as pathogenic for Tuberous Sclerosis Complex (TSC). TSC is a rare, autosomal dominant genetic disorder characterized by the growth of non-cancerous tumors, known as hamartomas, in various parts of the body, including the brain, kidneys, heart, eyes, lungs, and skin. Because TSC follows an autosomal dominant inheritance pattern, inheriting just one copy of the altered TSC1 gene from a parent is sufficient to increase the risk of developing the condition. Research indicates that while TSC2 mutations often result in a more severe clinical phenotype, TSC1 mutations like rs118203380 are still highly penetrant and clinically significant. The evidence linking this specific variant to TSC is considered moderate to strong in clinical catalogs, though the exact severity of symptoms can vary widely even among family members carrying the same genetic alteration.
Population Frequency and Ancestry
The rs118203380 variant is exceedingly rare in the general global population. Large-scale genomic databases, such as gnomAD and the 1000 Genomes Project, indicate that pathogenic mutations in the TSC1 gene occur at very low frequencies across all major ancestral groups. Tuberous Sclerosis Complex itself affects approximately 1 in 6,000 to 1 in 10,000 live births worldwide, and TSC1 mutations account for roughly one-third of all genetically identified TSC cases. Because rs118203380 is just one of thousands of possible mutations within the TSC1 gene, the specific frequency of this exact SNP is only a tiny fraction of that overall prevalence. There is currently no strong evidence to suggest that this specific variant is significantly more common in any one particular ethnic or ancestral population. Most individuals will carry the typical, non-mutated reference sequence at this genomic position.
What You Can and Cannot Do With This Information
Understanding your genotype at rs118203380 can provide valuable insights into your genetic predisposition for Tuberous Sclerosis Complex, but it is not a substitute for a formal medical diagnosis. If a direct-to-consumer DNA test indicates that you carry a pathogenic variant at this position, it is crucial to consult with a genetic counselor or a medical geneticist. They can help verify the results through clinical-grade testing, as third-party raw data analysis can sometimes yield false positives. Furthermore, while carrying this variant indicates a high statistical probability of developing TSC, it cannot predict the specific symptoms, their severity, or the age of onset. This educational information should never be used to self-diagnose or alter any medical treatments. Always discuss genetic findings and potential screening protocols with a qualified healthcare provider who can tailor a care plan to your personal and family medical history.
How common is this variant?
The rs118203380 variant is extremely rare across all global populations. Most individuals carry the typical reference alleles, and this specific pathogenic mutation is seen in only a tiny fraction of individuals diagnosed with Tuberous Sclerosis Complex.
Frequently asked questions
What is the TSC1 gene?
The TSC1 gene provides instructions for making a protein called hamartin. Hamartin works together with another protein, tuberin, to help regulate cell growth and division. When this gene is mutated, it can lead to uncontrolled cell growth and the formation of benign tumors.
What is Tuberous Sclerosis Complex (TSC)?
Tuberous Sclerosis Complex is a rare genetic disorder that causes non-cancerous tumors (hamartomas) to grow in various parts of the body. Common areas affected include the brain, skin, kidneys, heart, and lungs. Symptoms can range from mild skin abnormalities to severe neurological issues like seizures.
Does having the rs118203380 variant mean I definitely have TSC?
While the rs118203380 variant is classified as pathogenic and highly penetrant, having it does not serve as a clinical diagnosis on its own. However, it does indicate a significantly increased risk for the condition. You should consult a medical geneticist for clinical testing and a comprehensive evaluation.
Can TSC1 mutations be passed down to children?
Yes. TSC1 mutations follow an autosomal dominant inheritance pattern, meaning a person with the mutation has a 50% chance of passing it on to each of their children. A genetic counselor can help explain these risks and discuss family planning options.
Are mutations in TSC1 more severe than in TSC2?
Research generally suggests that mutations in the TSC2 gene are associated with a more severe clinical phenotype compared to TSC1 mutations. However, TSC1 mutations can still cause significant health issues, and the severity of symptoms can vary widely even among family members.
Sources & further reading
Educational information only, last refreshed 9/4/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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