MEFV rs121908007: Understanding Carrier Status
The rs121908007 variant is a specific genetic change in the MEFV gene that results in a missense mutation, where the amino acid methionine is replaced by isoleucine at position 680. This variant is primarily studied for its role as a carrier marker for familial Mediterranean fever (FMF), an autoinflammatory condition.
What each genotype means
Typical pyrin protein function
This genotype represents the common, non-variant form of the MEFV gene at this position. Individuals with this profile do not carry the specific p.Met680Ile variant associated with familial Mediterranean fever carrier status.
This is the most common genotype observed in all global populations.
Familial Mediterranean fever carrier
This genotype indicates you carry one copy of the p.Met680Ile variant. While familial Mediterranean fever is typically an autosomal recessive condition requiring two variants, carriers are generally asymptomatic, though the clinical significance of carrying a single variant remains a subject of ongoing research.
The allele frequency is approximately 0.002 in European non-Finnish and Middle Eastern populations, making this specific heterozygous genotype relatively rare.
Potential familial Mediterranean fever
This genotype indicates you carry two copies of the p.Met680Ile variant. Because familial Mediterranean fever is an autosomal recessive disorder, individuals with two variants in the MEFV gene may be at an increased risk for developing symptoms of the condition, though penetrance can vary significantly.
This homozygous genotype is extremely rare in the general population.
What is rs121908007?
The variant rs121908007, often referred to in clinical literature as p.Met680Ile or M680I, is a single nucleotide polymorphism located within the MEFV gene. This gene is situated on the short arm of chromosome 16. In this specific genetic change, a nucleotide substitution (c.2040G>C) alters the protein-coding sequence, leading to the substitution of the amino acid methionine with isoleucine at position 680 of the pyrin protein. This variant is one of several well-documented mutations in the MEFV gene that have been identified through clinical genetic testing. Because it is a missense mutation, it changes the primary structure of the resulting protein, which researchers study to understand how it might influence the protein's normal function in the body's inflammatory response pathways.
The Role of the MEFV Gene
The MEFV gene provides instructions for producing a protein called pyrin, also known as marenostrin. Pyrin is primarily expressed in white blood cells, specifically neutrophils, which are essential components of the innate immune system. Its main function is to act as a regulator of the inflammasome, a complex of proteins that triggers the body's inflammatory response. By controlling the activation of this complex, pyrin helps ensure that inflammation is appropriately managed and turned off when no longer needed. When mutations occur in the MEFV gene, the resulting pyrin protein may not function correctly, potentially leading to an overactive inflammatory response. This dysregulation is the underlying mechanism associated with familial Mediterranean fever, a condition characterized by recurrent episodes of fever and inflammation in the lining of the abdomen, lungs, or joints.
Research and Clinical Significance
Research into rs121908007 has largely focused on its status as a pathogenic variant associated with familial Mediterranean fever. Clinical databases, such as ClinVar, frequently classify this variant as pathogenic or likely pathogenic based on its presence in individuals diagnosed with FMF. Because FMF is inherited in an autosomal recessive pattern, an individual typically needs two pathogenic variants—one inherited from each parent—to manifest the full clinical symptoms of the disease. Consequently, individuals who carry only one copy of this variant are often identified as carriers. While carriers are generally asymptomatic, the clinical significance of carrying a single variant can vary based on family history and specific clinical presentation. It is important to note that the presence of this variant does not automatically result in a diagnosis, and clinical interpretation should always be performed by a qualified healthcare professional.
Population Frequency
The frequency of MEFV variants, including rs121908007, is notably higher in populations with ancestral ties to the Mediterranean basin, including individuals of Turkish, Arab, Jewish, and Armenian descent. In these groups, carrier rates for various MEFV mutations can be significantly higher than in the general global population. Data from resources like gnomAD indicate that the allele frequency for this specific variant in European non-Finnish and Middle Eastern cohorts is approximately 0.002. Because the prevalence of these variants correlates with Mediterranean ancestry, genetic screening is often more common in these specific demographic groups. Understanding these population-specific frequencies helps researchers and clinicians assess the likelihood of carrier status in different patient populations, though individual genetic testing remains the only way to confirm a person's specific genotype.
What This Information Means for You
If you have received information regarding your status for rs121908007, it is essential to understand that this is a genetic marker and not a medical diagnosis. Being a carrier for an autosomal recessive condition like FMF generally means you do not have the disease, but you may pass the variant to your children. This information is most relevant in the context of family planning or if you are experiencing unexplained symptoms that a doctor might want to investigate. You cannot use this information to self-diagnose or make decisions about medical treatments. If you have concerns about your genetic results or your family history, the most appropriate step is to consult with a genetic counselor or a physician who specializes in medical genetics. They can provide context based on your personal health history and help you understand the implications of your genetic profile.
How common is this variant?
The rs121908007 variant is most frequently observed in populations with Mediterranean ancestry, with an allele frequency of approximately 0.002 in European non-Finnish and Middle Eastern cohorts.
Frequently asked questions
Is rs121908007 the same as FMF?
No, rs121908007 is a specific genetic variant within the MEFV gene, while familial Mediterranean fever (FMF) is the clinical condition associated with certain mutations in that gene. Having the variant does not mean you have the disease, especially if you only carry one copy.
What should I do if I am a carrier?
If you are identified as a carrier, it is recommended to discuss this result with a genetic counselor or your primary care physician. They can help you understand what this means for your health and your family planning options.
Can I be tested for this variant?
Yes, this variant can be identified through clinical genetic testing, often as part of a panel for autoinflammatory diseases. You should speak with a healthcare provider to determine if such testing is appropriate for your situation.
Does this variant affect medication dosing?
There is no standard guidance linking this specific variant to medication dosing. Always discuss any concerns regarding medications or potential treatments with your clinician or pharmacist.
Sources & further reading
Educational information only, last refreshed 9/23/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Pathogenic missense variant in MEFV (p.Val726Ala) conferring carrier status or reduced-penetrance familial Mediterranean fever.
A missense mutation (c.2080A>G, p.Met694Val) in pyrin, a well-established pathogenic variant for familial Mediterranean fever (FMF) with high penetrance.
Missense substitution (c.2079A>G, p.Met694Ile) in MEFV associated with familial Mediterranean fever.
A missense substitution (c.2177T>C, p.Val726Ala) in MEFV establishing carrier status for autosomal recessive familial Mediterranean fever, common in Armenian and Arab lineages.
A missense substitution (c.1984G>A, p.Glu66Lys, often referred to as E148Q) associated with reduced penetrance for familial Mediterranean fever.
Carrier variant for Familial Mediterranean Fever (p.Met694Val), conferring carrier status for recurrent autoinflammatory febrile episodes.