TTR rs121912649 (V122I): Risk Variant for Amyloid Cardiomyopathy
The single nucleotide polymorphism rs121912649 in the TTR gene represents a missense variant historically known as Val122Ile (or p.Val142Ile). It is a well-characterized founder variant primarily identified in individuals of African and African American ancestry. Carrying this variant predisposes individuals to late-onset hereditary transthyretin amyloid cardiomyopathy, an infiltrative heart condition that typically manifests in older adulthood.
What each genotype means
Typical TTR gene profile
This genotype represents the common, non-amyloidogenic form of the TTR gene. It is not associated with the increased risk of hereditary transthyretin amyloid cardiomyopathy linked to the V122I variant.
This is the most common genotype across all global populations.
Increased amyloid cardiomyopathy risk
This genotype, often referred to as the V122I or p.V142I variant, is associated with an increased risk of late-onset hereditary transthyretin amyloid cardiomyopathy. Research indicates that this variant is primarily found in individuals of African ancestry and may be linked to more aggressive heart failure outcomes, though penetrance is variable. Please discuss your cardiovascular health and any symptoms with your clinician to determine if screening or monitoring is appropriate for you.
Carried by approximately 3% to 4% of individuals of African ancestry in the United States, and is generally rare in other populations.
Elevated amyloid cardiomyopathy risk
This genotype indicates that you carry two copies of the V122I (p.V142I) variant. While clinical data on homozygous individuals is limited, this variant is known to predispose individuals of African ancestry to hereditary transthyretin amyloid cardiomyopathy. You should discuss this finding with a cardiologist or genetic counselor to understand your specific health risks and appropriate clinical management.
This genotype is extremely rare, as the variant itself is primarily found in a heterozygous state in populations of African ancestry.
Genomic Location and Variant Characteristics
The rs121912649 variant is located on chromosome 18 within the TTR gene. At the nucleotide level, it typically involves a G to A transition (c.424G>A), resulting in the substitution of the amino acid valine with isoleucine at codon 122 of the mature transthyretin protein (or codon 142 when numbering includes the signal peptide, hence p.Val142Ile). Transthyretin functions as a tetrameric transport protein primarily synthesized by the liver, responsible for transporting thyroxine (vitamin A-binding complex carrier) throughout the bloodstream. The amino acid change caused by rs121912649 destabilizes this four-protein complex, making it prone to dissociating into individual monomers that misfold and aggregate into amyloid fibrils.
Biological Mechanisms and Amyloid Formation
Under normal physiological conditions, the transthyretin tetramer remains structurally stable. In carriers of the rs121912649 variant, the structural change accelerates the rate at which the tetramer breaks down into unstable dimers and monomers. These misfolded intermediates slowly self-assemble into insoluble amyloid fibrils that deposit within extracellular tissues. While some variants in TTR predominantly damage peripheral nerves, the amyloid fibrils generated by the V122I variant preferentially deposit within the myocardium (the heart muscle). Over decades, the accumulation of amyloid creates a stiff, thickened ventricular wall, impeding proper cardiac relaxation and leading to heart failure with preserved ejection fraction.
Clinical Evidence and Incomplete Penetrance
Multiple large-scale cohort studies, including the Atherosclerosis Risk in Communities (ARIC) study and biobank-linked analyses, associate the rs121912649 variant with an elevated risk of late-onset cardiomyopathy and congestive heart failure after age 50 to 60. ClinVar and medical genetic databases broadly classify this variant as pathogenic for autosomal dominant hereditary transthyretin amyloidosis. However, clinical penetrance is incomplete and age-dependent: not every individual who inherits the variant will go on to develop clinical amyloidosis or heart failure. Environmental factors, modifier genes, sex, and age significantly influence whether an individual remains an asymptomatic carrier or develops progressive heart disease.
Population Distribution and Founder History
The rs121912649 variant is a classic example of ancestral population enrichment. Molecular epidemiology indicates that the variant originated in coastal West Africa. Consequently, it is observed at relatively high carrier frequencies in West African populations and the African diaspora, including approximately 3% to 4% of African Americans (gnomAD minor allele frequency roughly 0.015 to 0.020). By contrast, it is exceptionally rare in populations without African genetic admixture. Because symptoms often masquerade as conventional hypertensive heart disease or non-amyloid heart failure in elderly populations, the medical community recognizes that conditions linked to this variant have historically experienced substantial underdiagnosis.
Interpreting Results and Clinical Perspective
Learning about an rs121912649 result through personal genomic screening is informative for risk awareness, but it does not represent a medical diagnosis. Genetic results alone cannot establish whether amyloid accumulation is actively occurring. If a person carries the variant, clinical evaluations such as echocardiograms, cardiac MRI, or nuclear scintigraphy (technetium pyrophosphate scans) are the standard diagnostic tools used by cardiologists to evaluate heart structure. Modern medical management includes specific therapies, such as transthyretin tetramer stabilizers, aimed at halting fibril deposition. Individuals with questions regarding personal or family risk should consult a cardiologist or certified genetic counselor.
How common is this variant?
The rs121912649 alternative allele is predominantly enriched in individuals of African ancestry, where the minor allele frequency in gnomAD is approximately 0.015 to 0.020 (representing a carrier frequency of about 3% to 4% in African Americans), while it is virtually absent in non-admixed European, Asian, and other global populations.
Frequently asked questions
Does having the rs121912649 variant mean I will definitely develop heart failure?
No. The variant exhibits incomplete, age-dependent penetrance, meaning many people carry the allele throughout their lives without ever experiencing amyloid-related heart symptoms. While it elevates statistical risk, it does not guarantee disease development.
What is the difference between V122I and p.Val142Ile?
They refer to the exact same genetic change. 'V122I' follows the historical numbering of the mature transthyretin protein, whereas 'p.Val142Ile' reflects modern standard HGVS nomenclature that counts the initial 20-amino-acid signal peptide.
How do doctors check for transthyretin amyloidosis?
Physicians evaluate suspected cases using specialized cardiac imaging, including echocardiograms, cardiac magnetic resonance imaging, and non-invasive bone scintigraphy (PYP scans) that detect amyloid deposits in the heart muscle.
Are treatments available if someone develops symptoms?
Yes, several pharmacological therapies, including transthyretin stabilizers like tafamidis, are available to slow or prevent disease progression by binding to and stabilizing the transthyretin protein complex.
Sources & further reading
Educational information only, last refreshed 9/5/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Causes the classic p.Val50Met (historically Val30Met) pathogenic substitution responsible for familial amyloid polyneuropathy and hereditary transthyretin amyloidosis (ATTR).
Transthyretin missense variant p.Val142Ile (V122I) associated with hereditary transthyretin amyloid cardiomyopathy.
Pathogenic missense variant (p.Val142Ile / V122I) in TTR responsible for hereditary transthyretin amyloid cardiomyopathy.
Pathogenic missense variant (commonly designated Val30Met or p.Val50Met) associated with hereditary transthyretin-mediated amyloidosis.
Causes hereditary transthyretin amyloidosis (V122I), common in African Americans.