Dr. Witteles, a cardiologist and co-director of the Stanford Amyloid Center, discusses genetic testing, sequencing the TTR gene, and clarifies the confusing mutation nomenclature. He details the most common of the more than 145 known hereditary mutations, the prevalence of cardiomyopathy versus neuropathy, and references studies around diagnostic factors.
The treatment for patients with Transthyretin Cardiac Amyloidosis has advanced significantly since 2018 when there were no FDA-approved therapies. In this presentation, Dr. Mat Maurer from Columbia University shares how diagnostic imaging techniques have significantly improved, thereby reducing the need for an invasive heart biopsy. In addition, he shares fascinating statistics on how the age and stage of diagnosis has been evolving. Based on today’s clinical trials, providers are optimistic that the expansion of options for patient care will continue.
The future is indeed looking brighter.
Patients with ATTR amyloidosis are commonly faced with neurological complications. In this presentation, Dr. Chafic Karam from the University of Pennsylvania goes through four areas: an overview of the neurological systems, how amyloid damages the nerves, neurological signs of ATTR amyloidosis, and how to detect amyloid and diagnose ATTR amyloid neuropathy.
Dr. Sarah Lee, Assistant Professor of Medicine at the University of Washington, provides a brief clinical overview of amyloidosis.
Amyloidosis can present in many types with the three most prevalent being light chain (AL) amyloidosis, hereditary variant transthyretin (ATTRv) amyloidosis, and wild type transthyretin (ATTRwt) amyloidosis. Being a rare disease, diagnosis can be particularly challenging, given that the general medical community is not well educated on the malady and symptoms are often associated with other more common ailments.
Successfully diagnosing the disease requires a two-step process before an appropriate treatment program can be determined and implemented for each patient.
- First, if amyloidosis is suspected, testing must be done to confirm the presence of amyloid.
- Second, once the presence of amyloid is confirmed, testing must then be done to identify and confirm the type of amyloidosis.
It is crucial that the second step, where the correct type of amyloidosis is identified, as the treatment regime can be different for each type. Here we share two different patient experiences which illustrate successful execution of the two-step diagnostic process.
Patient Case #1
The first case involved a 23-year old female. In 2017 she experienced an episode of coughing up blood, after which she looked in her throat with a flashlight and discovered a sizable lump. The patient met with a local ENT, who incorrectly diagnosed allergies, and prescribed over-the-counter medicine. With no improvement, she met with a second ENT. Testing was performed on the patient’s left oral pharynx utilizing a Congo red staining biopsy process which confirmed the presence of amyloid in the tissue. Additionally, mass spectrometry was performed which successfully differentiated the type of amyloidosis as being ALH (lambda light chain and delta heavy chain). Subsequently, she was referred to a hematologist who ordered a bone marrow biopsy and blood testing. The bone marrow biopsy summary notes read “….in conjunction with the concurrent finding of monoclonal lambda light chain restricted plasma cells in the marrow by flow cytometry, the findings are consistent with involvement of the marrow by a plasma cell neoplasm.”
Additionally, the blood testing confirmed elevated light chains as shown below.
Patient Case #2
The second case involved a man in his mid-fifties. He began experiencing disease symptoms approximately 6-7 years prior to being diagnosed in early 2019. He initially experienced gradually progressing numbness in his feet, legs, hands and forearms, as well as bilateral carpal tunnel syndrome. Soon after, he began experiencing symptoms of lightheadedness and fainting. Additionally, he started experiencing progressive gastro-intestinal issues such as acid reflux, chronic coughing, and frequent bouts of constipation and diarrhea. By 2018, his physical condition was rapidly deteriorating, including a total weight loss of approximately 80 pounds. During this extended period of time he was seen by a variety of physicians including internal medicine, neurology, endocrinology, gastroenterology, oncology, and cardiology, none of who were successful in arriving at a conclusive diagnosis. His list of maladies included cardiomyopathy, peripheral neuropathy, autonomic neuropathy, bilateral carpal tunnel syndrome, and gastroparesis, all which are classic symptoms of amyloidosis.
Finally, in early 2019 his condition was successfully diagnosed by an amyloidosis specialist. An echocardiogram was performed as well as a cardiac MRI (utilizing a gadolinium tracer) to identify amyloid fibrils and related damage in the heart tissue. These tests confirmed the presence of amyloid. A free light chain serum test was performed which ruled out AL amyloidosis, and Transthyretin DNA sequencing was performed to differentiate between the hereditary variant and wild-type of ATTR, which identified the T80A (legacy T60A) variant of transthyretin (ATTRv) amyloidosis. The two tests were successful in identifying the type of amyloidosis. The associated testing results are show below.
Echocardiogram Summary Notes
Associated Cardiac MRI Interpretation
DNA Sequencing Result
Once Diagnosed, Next is a Treatment Plan
Once the presence of amyloid is confirmed, and the type is identified, then it is time to treat the disease. In each of these patient cases the disease was diagnosed utilizing the two-step process to identify and confirm the type of amyloidosis. In both cases, successful treatment regimens were implemented which were effective in putting the disease into remission and/or halting disease progression.
Treatment options for amyloidosis have been vastly improved over the past several years. What was previously considered to be a foregone fatal disease can now be a manageable chronic disease. To ensure the best patient outcome, a timely diagnosis utilizing the two-step process, is essential.
Amyloidosis is a multi-system disease, making diagnosis challenging. In this informative patient guide, the American Society of Nuclear Cardiology (ASNC) discusses common symptoms, types of amyloidosis, red flags to be aware of, diagnostic tests and available treatment options.
CLICK HERE to read/download ASNC’s Guide for Understanding Amyloidosis
Multi-systemic diseases such as amyloidosis are complex to diagnose, but also complex in treatment and ongoing patient care. It takes a village. In this seminal piece, the American College of Cardiology (ACC) provides an Expert Consensus Decision Pathway on Comprehensive Multidisciplinary Care for the Patient With Cardiac Amyloidosis.
According to Dr. Vaishali Sanchorawala, Director of the Amyloidosis Center at Boston Medical Center, “The results and progress in the therapeutic landscape of systemic amyloidosis are unbelievable, unprecedented and unheard of for this uniformly fatal disease of the 1990s. But they are not enough, and therefore we need to work together to make a difference.”
This paper is an absolute must-read for cardiologists and other specialties such as neurology, gastroenterology, nephrology and hematology. To read, click on the image below.
Kittleson M, Ruberg F, et al. 2023 ACC Expert Consensus Decision Pathway on Comprehensive Multidisciplinary Care for the Patient With Cardiac Amyloidosis. J Am Coll Cardiol. 2023 Mar, 81 (11) 1076–1126.
Hereditary Amyloidosis in Black Americans of African Descent: ATTR V122I Variant
Amyloidosis, still considered a relatively rare disease, can take several forms. Each slightly different, but most sharing similar debilitating symptoms of cardiac and/or neurological impairment, or both. It is viewed by many experts that amyloidosis has been presenting in plain sight and missed, or wildly underdiagnosed, for decades and, in some cases, generations. Thankfully, education to raise awareness within the healthcare community, along with improvements in diagnostic tools and testing, the journey to diagnosis and treatment is becoming more visible.
The hereditary transthyretin amyloidosis (hATTR) type results from a genetic mutation of a protein, transthyretin, which is produced in the liver and circulates throughout the body. The mutation causes the TTR protein to misfold, becoming unstable and depositing in organs and nerve systems causing impairment and eventual organ failure. Common symptoms for the disease include bilateral carpel tunnel syndrome, muscle weakness, cardiomyopathy, polyneuropathy, GI issues especially chronic diarrhea and constipation, and both nuisance and serious concerns and if untreated can lead to death. Early diagnosis, genetic testing to identify the exact genetic mutation, and treatment are important to slow the progression of the disease and conserve quality of life.
Considered a rare disease, advances in diagnosis have shown that it is less rare than originally thought.
Familial amyloidosis caused by a transthyretin mutation occurs in approximately 1 in 100,000 Caucasians in the U.S, and more commonly in African Americans (approximately 4% in that population). This condition is prevalent in Portugal, Sweden, Japan, Ireland, Spain, France, Finland, Germany and Greece. Symptoms usually begin between 40 and 65 years of age.
To date over one hundred variants of TTR have been identified as causing ATTR amyloidosis and they are distributed worldwide with concentrations in various ethnic populations. One variant, V122I is most commonly found in people with African and especially West African ancestry. It has been distributed worldwide but especially in North America and the Caribbean through historic slave trade and the migration of populations. This variant is most often associated with ATTR-CM (Amyloidosis with cardiomyopathy) and heart failure.
Worldwide Carrier Rates of TTR V122I in Self-Reported Countries/Regions
From Multicenter Study JAMA 2019 Dec 10;322(22):2191-2202.
In an article by J. Buxdaum and F. Ruberg in the Journal Genetics in Medicine January 2017, the authors stated the following findings.
Since the identification of a valine-to-isoleucine substitution at position 122 (TTR V122I; pV142I) in the transthyretin (TTR)-derived fibrils extracted from the heart of a patient with late-onset cardiac amyloidosis, it has become clear that the amyloidogenic mutation and the disease occur almost exclusively in individuals of identifiable African descent. In the United States, the amyloidogenic allele frequency is 0.0173 and is carried by 3.5% of community-dwelling African Americans. Genotyping across Africa indicates that the origin of the allele is in the West African countries that were the major source of the slave trade to North America. At autopsy, the allele was found to be associated with cardiac TTR amyloid deposition in all the carriers after age 65 years; however, the clinical penetrance varies, resulting in substantial heart disease in some carriers and few symptoms in others. The allele has been found in 10% of African Americans older than age 65 with severe congestive heart failure. At this time there are potential forms of therapy in clinical trials. The combination of a highly accurate genetic test and the potential for specific therapy demands a greater awareness of this autosomal dominant, age-dependent cardiac disease in the cardiology community.
Genet Med advance online publication 19 January 2017
The prevalence and distribution of the amyloidogenic transthyretin (TTR) V122I allele in Africa.
1:CAS:528:DC%2BC28XhsFSlsbfJ 10.1002/mgg3.231 Mol Genet Genomic Med. 2016; 4: 548-556
Dr. Martha Grogan, director of the Cardiac Amyloid Clinic of Mayo Clinic in Rochester, Minnesota commented in an interview published in the Mayo News Network (https://newsnetwork.mayoclinic.org/discussion/expert-alert-cardiac-amyloidosis-masquerades-as-other-conditions-1-type-affects-more-black-americans/) that amyloidosis can be tricky to suspect because symptoms may not be initially present and they may mimic other more common diseases. Currently there are options for free saliva or blood tests through several pharmaceutical companies. To determine the type of the disease genetic testing is important.
The University of Pennsylvania and the Icahn School of Medicine at Mount Sinai conducted a study of 52,492 participants of which 11,143 were of self-reported African ancestry. https://jamanetwork.com/journals/jama/fullarticle/2757227
An excellent discussion of the results emphasizes the conclusion that a significant association of TTR V122I and heart failure in the tested population, primarily in those of West African ancestry, exists. In addition, they confirm previous studies that have suggested a high rate of underdiagnosis of hATTR-CM in cases of cardiomyopathy and heart failure in elderly patients of African Ancestry. The discussion further suggests that this is likely due to lack of information and familiarity with the disease in the medical community.
CITATION: Damrauer SM, Chaudhary K, Cho JH, et al. Association of the V122I Hereditary Transthyretin Amyloidosis Genetic Variant With Heart Failure Among Individuals of African or Hispanic/Latino Ancestry. JAMA. 2019;322(22):2191–2202. doi:10.1001/jama.2019.17935. https://pubmed.ncbi.nlm.nih.gov/31821430/
Discussion of a different study of 7,514 African American participants in the US considered the question of the association between genetic variation and the risk of heart failure. This study was conducted by the University of Alabama, University of Colorado, Columbia University, and Cornel University. The results are similar to those in the University of Pennsylvania study discussed above, with additional comments that more subtle symptoms and changes may be apparent well before the typical onset of significant disease, average age 65, and the need for earlier screening for early detection and treatment.
An autosomal-dominant disease, hATTR-CM has a median survival of nearly 2.5 years without treatment after receiving a diagnosis.34,35 Extrapolating the hATTR-CM–associated Val122Ile variant frequency to the population level suggests that approximately 1.4 million Black individuals carry this variant implicated in the development of heart failure and reduced overall survival. Despite the possible clinical implications, the Val122Ile TTR variant, which is seen relatively more commonly among individuals of African ancestry, is not included in the list of clinically actionable deleterious variants compiled by the American College of Medical Genetics and Genomics.9 Thus, this potentially deleterious variant may not be reported as clinically actionable, thereby reducing physician vigilance for hATTR-CM.
Findings In this retrospective cohort study that included 7,514 Black participants in the US with a median 11.1 years of follow-up, the incidence of heart failure was 15.6 per 1000 person-years among Val122Ile variant carriers compared with 7.2 per 1000 person-years among noncarriers, with an adjusted hazard ratio of 2.43.
Meaning Being a carrier of the Val122Ile variant was significantly associated with an increased risk of heart failure among Black individuals living in the US.
CITATION: Parcha V, Malla G, Irvin MR, et al. Association of Transthyretin Val122Ile Variant With Incident Heart Failure Among Black Individuals. JAMA. 2022;327(14):1368–1378. doi:10.1001/jama.2022.2896
Despite the evidence that a meaningful 3-4% of the US Black population of West African ancestry likely carries the V122I genetic mutation, hereditary TTR amyloidosis remains significantly underdiagnosed and undertreated in this population.
Cardiac symptoms in elderly black patients have too often been treated for more common cardiomyopathy and heart conditions, resulting in lack of appropriate treatment and often death. Because of lack of awareness in the medical community and reduced access to expert medical care, more subtle symptoms in younger black patients generally have not caused the physicians to consider amyloidosis. Additionally, lack of genetic testing can mean that entire families are unaware of the implications of the disease.
Amyloidosis can be devastating to both patients and their families. Increased awareness of the disease, availability of testing, and FDA-approved therapies are slowly beginning to shift this dynamic. However, there is still much work to be done to close the gap between diagnosed cases and the population estimated to be affected.
Early diagnosis is key.
For additional information regarding hereditary amyloidosis:
Amyloidosis is a group of diseases that have a common feature where proteins behave abnormally, with the breakdown products of these proteins folding upon themselves and depositing in various organs. Hereditary transthyretin amyloidosis is caused by a genetic mutation which causes misfolding of transthyretin (TTR) proteins (which originate from the liver). There are over 100 genetic variants of hereditary amyloidosis.
One such variant, called T60A, is the most common variant in Ireland (and the UK).
Symptoms of hereditary amyloidosis, specifically the T60A variant, include a variety of peripheral neuropathic, autonomic, and cardiac maladies, including:
- carpal tunnel syndrome
- numbness and tingling in hands, feet, arms, and legs
- muscular weakness
- excessive sweating
- dizziness/fainting (orthostatic hypotension)
- sexual disfunction
- unintentional weight loss
- acid reflux
- bouts of constipation and diarrhea
- shortness of breath
- leg swelling
- chest pain
One Patient’s Story
“Do you have an ancestor from Donegal?” is a question frequently asked by doctors who are investigating the possibility that a patient may have hereditary amyloidosis type T60A. With its origins in a short ribbon of coastline in North-West Donegal (Ireland), the condition wandered worldwide with Irish migration.”
(Callaghan, Donegal Amy, 2022.)
Donegal Ireland was one of the worst affected areas of Ireland’s “Great Hunger” of the mid to late 1800’s. 123,000 emigrants left the Donegal area between 1851-1900. A great many of them migrated to the United States, many to the Appalachian region of the country. The T60A variant, as it now appears in the United States, has been traced back to those settling in Appalachia. Sean Riley is a T60A amyloidosis patient who has ancestorial connections to Appalachia and the Donegal area.
Sean’s journey to diagnosis began in the fall of 2012 when he had bilateral carpal tunnel surgery. His job required quite a bit of typing and handwriting so he assumed that the condition was related to repetitive motion, which is a common cause of carpal tunnel syndrome. Little did he or the attending hand surgeon know that bilateral carpal tunnel syndrome may be an early neurological symptom of amyloidosis.
Concurrently, Sean started experiencing numbness in his left foot and lower left leg. He previously had vascular surgery on the left leg, and incorrectly assumed that the foot and leg numbness might be associated with nerve damage from the surgery. In actuality the numbness was due to the onset of peripheral neuropathy, yet another early symptom of the disease.
Between 2014 and 2017 he was taken to the hospital by ambulance on three separate occasions. In each instance he felt extreme dizziness and discomfort in his chest and assumed that the events were due to a cardiac issue, but no obvious signs of cardiac issues could be identified in any of the events. He now knows that what he was experiencing was orthostatic hypotension due to the onset of progressive autonomic neuropathy, another signature malady associated with the disease.
In the fall of 2017 Sean started being treated for severe acid reflux and gastrointestinal issues. Over time he had an endoscopy and colonoscopy performed, each which indicated normal results. These conditions likely indicated the onset of amyloidosis impact on nerves and tissue of the gastro-intestinal system.
Over the period of time from 2012 through 2017 Sean was seen by a hand surgeon, cardiology, oncology, endocrinology, neurology, and gastroenterology, along with his primary care physician. Nobody was able to connect the dots to amyloidosis, a product of the rarity of the disease and resulting lack of disease expertise by the general medical community.
In 2018 Sean moved overseas to Abu Dhabi to pursue a career opportunity. Shortly after arriving he started experiencing more frequent hypotensive episodes as well as progressive muscle wasting and weight loss. Fortunately for Sean the Cleveland Clinic has a hospital facility in Abu Dhabi. The attending cardiologist had a working knowledge of amyloidosis and ordered a series of tests, including an echocardiogram, a cardiac MRI, and a neuropathic evaluation, all of which concluded a preliminary positive diagnosis for the disease. As a result, the cardiologist recommended that Sean travel back to the United States and be seen at the amyloidosis center at Brigham and Women’s hospital in Boston. In February of 2019 he received a definitive diagnosis of hereditary transthyretin amyloidosis, specifically the T60A mutation. Excerpts of the confirming echocardiogram, cardiac MRI, and genetic testing results are shown below.
Shortly after diagnosis, Sean started treatment with a state-of-the-art FDA-approved amyloidosis drug. The treatment is administered every three weeks and is designed to slow or stop disease progression. The drug is an RNA signal blocker which stops the transthyretin proteins from misfolding and creating amyloid fibrils.
Sean continues this therapy to this day, and all indications show that disease progression has stopped. There is no cure for the disease, so he must contend with and manage the damage that has been done; however, he is thrilled that the disease progression is being kept in check.
For more information on hereditary amyloidosis worldwide, visit our blog — Click Here
“Donegal Amy-A Rare Inherited Disease from Ireland”, Rosaline Callaghan, Roscara Books, 2022.
“Unraveling the Lineage: The Genetic Basis of Familial ATTR Cardiomyopathy Ronald Witteles”, MD Professor of Medicine (Cardiovascular Medicine).
“Cardiac Amyloidosis Part 1: Understanding Types and Risks”, Dr. Rodney Falk, Brigham and Women’s Hospital, YouTube, July 2018.
- Obi CA, Mostertz WC, Griffin JM, Judge DP. ATTR Epidemiology, Genetics, and Prognostic Factors. Methodist Debakey Cardiovasc J. 2022 Mar 14;18(2):17-26. doi: 10.14797/mdcvj.1066. PMID: 35414855; PMCID: PMC8932385.
Transthyretin Amyloidosis, or ATTR, is considered a single disease, however the diversity in its clinical presentation is staggering. In this blog, we’ll discuss some of the most common hereditary variants and how the disease manifestation differs around the world in documented hotspots.
Source: Epidemiology, Genetics, and Prognostic Factors (1)
There are two distinct forms of Transthyretin Amyloidosis (ATTR), the hereditary form (ATTRv), and the non-hereditary form (ATTR-wt) commonly referred to as wild-type amyloidosis. Disease manifestation is considered a spectrum involving aspects of cardiomyopathy, neuropathy, or more frequently a mixture of both.
Below we’ll discuss the hereditary form and the various genetic variants and how they differ based on geographical location.
WHAT IS TRANSTHYRETIN (TTR)
Transthyretin, also known as prealbumin, is a protein produced primarily in the liver that is responsible for the transport of thyroxine and retinol. Interesting enough, this is how it got its name.
In steady state, the protein circulates primarily as a tetramer (i.e., monomeric form), but unfortunately, its monomeric form is inherently amyloidogenic (prone to breakdown and formation of amyloid aggregates). Couple that with mutations that increase the amyloidogenicity of the protein, these tetramers dissociate into monomers that will misfold, aggregate, and form the insoluble fibrils (“amyloid”) that are resistant to the body’s inherent protective mechanisms like proteolysis.
SPECIFIC TTR PATHOGENIC VARIANTS
As of today, there have been over 145 reported variants related to hereditary transthyretin amyloidosis. Interestingly, these genetic variants have a tendency to cluster in both geographic and ethnic groups around the world. We’ll discuss some of the most prevalent mutations below.
This is the most common TTR mutation in the United States, with a prevalence of roughly 3.4% in the African American community. The disease is primarily cardiac in nature, typically present when patients are in their 60s. It is thought that this mutation arose from the region of West Africa and has worked its way to the United States over time, where it has become the predominant form.
This is the most commonly recognized TTR mutation worldwide and the first TTR variant discovered. It is most commonly found in the regions of Portugal, Spain, France, Japan, Sweden, and Brazil. Interestingly, between these regions where this mutation dominates, there is variability in age of onset and parent-of-origin. For example, age of onset was found to be earlier in the Swedish population in comparison to Portugal and Japan. As for the parent-of-origin, it was found that the mother was more likely than the father to pass along the mutation (153 vs. 138), whereas in the French population the father was more likely to pass on the mutation (219 vs. 216), although not by much. The one thing these populations do have in common is this form of the disease is almost exclusively neurologic in nature.
This variant is most commonly found in the UK and Irish populations, and is also seen in the Appalachian region of the United States. This variant presents as a mixture of both cardiomyopathy and neuropathy symptoms. It seems to be that in early stages of the disease the neurologic symptoms are most prevalent, but cardiac symptoms present at diagnosis seem to indicate poorer patient outcomes.
This is arguably the most interesting variant that was investigated in a large study of the Danish population. The presence of this mutation actually confers a protective benefit. When this mutation occurs along with the Val30Met mutation, it has the effect of stabilizing and delaying, even preventing transthyretin amyloidosis.
While the prognosis is by no means near perfect, it is improving. There is continued advancement in the field of transthyretin amyloidosis, whether it be improving diagnostic methods, drug development, or a potential cure on the horizon with CRISPR gene-editing technology. Having said that, there continue to be significant barriers to diagnosis. The importance of being an astute clinician to suspect and work up for amyloidosis remains at the forefront of the challenge.
The geographic nature of this disease plays an important role in identifying and diagnosing amyloidosis. Having an understanding of how the presentation of the disease is heavily related to the patient’s ancestry and location around the world. The hardest part is suspecting amyloidosis, from there don’t forget the value of the diagnostic tools at your disposal, including genetic testing. Use this knowledge to strengthen and guide your suspicions of amyloidosis!
Over the upcoming months we’ll post blogs delving deeper into some of these variants, so stay tuned.
Thanks for reading,
Obi CA, Mostertz WC, Griffin JM, Judge DP. ATTR Epidemiology, Genetics, and Prognostic Factors. Methodist Debakey Cardiovasc J. 2022 Mar 14;18(2):17-26. doi: 10.14797/mdcvj.1066. PMID: 35414855; PMCID: PMC8932385.