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Neuropathy, also known as peripheral neuropathy, is a broad term that is used to describe damage to the nerves outside of the brain and spinal cord. There are over 100 types of peripheral neuropathy that can be classified into four categories, with each type having their own symptoms and prognosis. In this article, we’ll discuss the types of peripheral neuropathy and its connection to amyloidosis.

Symptoms

One of the challenges with neuropathy is the fact that symptoms can vary significantly based on what nerve is damaged. Additionally, symptoms can develop over the course of months to years (chronic neuropathy) or come on suddenly (acute neuropathy). Some of the most commonly seen symptoms are listed below:

Muscle weakness
Cramps
Muscle twitching
Loss of muscle and bone
Changes in skin, hair, or nails
Numbness
Loss of sensation or feeling in body parts
Loss of balance or other functions as a side effect of the loss of feeling in the legs, arms, or other body parts
Emotional disturbances
Sleep disruptions
Loss of pain or sensation that can put you at risk, such as not feeling an impending heart attack or limb pain
Inability to sweat properly, leading to heat intolerance
Loss of bladder control, leading to infection or incontinence
Dizziness, lightheadedness, or fainting because of a loss of control over blood pressure
Diarrhea, constipation, or incontinence related to nerve damage in the intestines or digestive tract
Trouble eating or swallowing
Life-threatening symptoms, such as difficulty breathing or irregular heartbeat

Types of Neuropathy

Motor Neuropathy → Damage to the motor nerves control how you move.
Sensory Neuropathy → Damage to sensory nerves control what you feel.
Autonomic Nerve Neuropathy → Damage to autonomic nerves that control functions that are involuntary (ie. you do not consciously control).
Combination Neuropathies → Damage to a mix of 2 or 3 of these other types of neuropathies. For example, damage to both sensory and motor nerves would result in sensory-motor neuropathy.

Amyloidosis

Peripheral Neuropathy is one of the hallmarks of amyloidosis, often seen in the transthyretin form of amyloidosis (ATTR). ATTR-PN, or transthyretin amyloid polyneuropathy, is a disease where the transthyretin protein becomes unstable and misfolds. This unstable protein (“amyloid”) then deposits in the nerve tissue, resulting in damage to these nerves. While amyloid deposits primarily in the peripheral nerves, it is not uncommon for amyloid deposition in the autonomic nerves as well.

While peripheral neuropathy is most commonly associated with ATTR amyloidosis, it should be noted that peripheral neuropathy is also seen in 15-35% of patients with AL amyloidosis.

Most importantly, these are the most common and important signs and symptoms to be aware of, in order to diagnose ATTR amyloidosis.

Neurological Complications of ATTR Amyloidosis

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.

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References:

https://my.clevelandclinic.org/health/diseases/14737-neuropathy

https://www.hopkinsmedicine.org/health/conditions-and-diseases/peripheral-neuropathy

https://www.mayoclinic.org/diseases-conditions/peripheral-neuropathy/symptoms-causes/syc-20352061

https://practicalneurology.com/articles/2021-july-aug/neuromuscular-amyloidosis

https://healthjade.net/familial-amyloidosis/

Cardiomyopathy is a broad term that is used to describe disease of the heart muscle, making it difficult for the heart to provide the body with an adequate blood supply. It can lead to heart failure and even death. In this article, we’ll discuss the types of cardiomyopathy and its connection to amyloidosis.

Risk Factors

It has no ideal target, as it can affect a person of any age, race, or gender. However, there are a number of risk factors that can put one at an increased chance of developing cardiomyopathy.

Genetic History → Family history of cardiomyopathy, heart failure, or sudden cardiac arrest
High Blood Pressure → Over a long period of time
Heart Conditions → Past history of heart attack, coronary artery disease, or infection of the heart
Obesity → Tends to make the heart work harder to perform its normal function
Alcohol Use → Long period of alcohol use
Drug Use → Use of illicit drugs, such as cocaine, amphetamines, and anabolic steroids
Medications → Drugs used in the treatment of cancer, such as chemotherapy and radiation

Additionally, there are a number of diseases that increase the risk of developing cardiomyopathy, including:

Amyloidosis
Connective Tissue Disorders
Diabetes
Hemochromatosis (excess iron storage)
Sarcoidosis
Thyroid Disease

Types of Cardiomyopathy

Dilated Cardiomyopathy → Dilation of the left ventricle prevents the heart from pumping effectively. It most commonly occurs in middle-aged men and is typically the result of coronary artery disease, heart attack, or genetic defects.

Hypertrophic Cardiomyopathy → Abnormal thickening of heart muscle, most commonly affecting the muscles surrounding the left ventricle. This type of cardiomyopathy is strongly associated with a family history of the disease. There have been genetic mutations linked specifically with this type of cardiomyopathy.

Restrictive Cardiomyopathy → Stiffening of the heart muscle results in an inelasticity, making it difficult for the heart to expand and fill. It is most commonly seen in the elder population. The disease can be of idiopathic origin or of disease such as amyloidosis. This is the least common type of cardiomyopathy.
Arrhythmogenic Right Ventricular Dysplasia → Scar tissue replaces healthy tissue of the right ventricle. This form of cardiomyopathy is rare and often the result of genetic mutations.
Unclassified Cardiomyopathy → All other forms of cardiomyopathy fall within this category.

Amyloidosis

Cardiomyopathy is one of the hallmarks of amyloidosis, often seen in the transthyretin form of amyloidosis (ATTR). ATTR-CM, or transthyretin amyloid cardiomyopathy, is a disease where the transthyretin protein becomes unstable and misfolds. This unstable protein (“amyloid”) then deposits in the heart muscle, resulting in thickening and stiffening of the heart.

The two types of ATTR-CM are wild-type ATTR-CM (wtATTR) or hereditary ATTR-CM (hATTR). wtATTR-CM is the most common form of ATTR-CM, affecting predominantly white males 60+ years old. hATTR-CM is genetic affecting both men and women, and presents as early as 50+ years old. Interestingly, one of the mutations causing hATTR, V122I, is seen almost exclusively in individuals of African ancestry. It is believed that approximately 3-4% of African Americans carry this mutation, regardless of whether or not they develop symptoms.

Most importantly, these are the most common and important signs and symptoms to be aware of, in order to diagnose ATTR amyloidosis.

Expert Insights – Cardiac Clues and Clinical Signs

In part 1 of a 2-part series, Dr. Keyur Shah, cardiologist from VCU Health’s cardiac amyloidosis care team, discusses the two most common types of transthyretin (TTR) amyloidosis: hereditary and wild-type. He details how ATTR cardiomyopathy amyloidosis presents and manifests itself to impair the heart. Dr. Shah lists clinical clues, “red flags,” and biomarkers which can raise suspicion of the presence of amyloidosis. Next he discusses insights that can be gained from echocardiograms, electrocardiograms, and cardiac MRIs and how they offer possible indicators of the disease presence. Once amyloidosis is suspected, definitive diagnosis testing is next.

In part 2 of a 2-part series, Sarah Paciulli, Heart Failure Nurse Practitioner, from VCU Health’s cardiac amyloidosis care team, continues from where Dr. Keyur Shah ended in Part I and discusses here in Part II the non-cardiac clues of transthyretin (TTR) amyloidosis. She expands the list of clinical clues and “red flags” that clinicians should be alert to, including orthopedic manifestations, erectile dysfunction, and polyneuropathy.

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References:

https://www.mayoclinic.org/diseases-conditions/cardiomyopathy/symptoms-causes/syc-20370709

https://www.yourheartsmessage.com

https://healthjade.net/familial-amyloidosis/

Dr. Sarah S. Lee, Assistant Professor, Division of Hematology, at the City of Hope, provides a brief yet comprehensive clinical overview of amyloidosis. In this video Dr. Lee discusses the breadth of amyloidosis, the wide range of symptom presentations, and which organs are typically involved. Focusing on AL (light chain) and TTR (transthyretin) types, she then goes through a diagnostic workup to arrive at a diagnosis, stressing the importance of typing once the presence of amyloid has been confirmed. Concluding her overview, Dr. Lee describes treatments available and how they impact patient prognosis and quality of life.

Often called “Popeye Deformity,” bicep bunching is visible when the patient flexes their arm, giving the appearance of Popeye-like arms. While it is the result of a torn tendon, it can be a leading indicator of more serious issues.

WHAT IS IT?

When the bicep tendon is ruptured, patients develop a bunching of the biceps upon flexion of the arm against gentle resistance. Tendon ruptures occur largely in the dominant arm of each patient, with one-quarter of patients developing ruptures in both arms. Interestingly, of those who had a rupture, 37.8% didn’t know it.

Below watch a video from The Lancet showing what bicep bunching looks like.

WHAT DOES IT POTENTIALLY INDICATE?

Two things.

1. Bicep bunching may be a marker for ATTRwt. According to MedPage Today, spontaneous ruptures of the distal biceps tendon may be a marker of wild-type transthyretin (TTR) cardiac amyloidosis, a single-center study found. The presentation of a tendon rupture, an easily elicited diagnostic sign, in a patient with HFpEF should raise suspicion for wild-type TTR cardiac amyloidosis.

The picture below (Source: JAMA September 12, 2017 Volume 318, Number 10) offers examples of ruptured biceps tendon in two patients with biopsy-proven ATTRwt Cardiac Amyloidosis. ATTRwt indicates wild-type transthyretin amyloidosis. Patient 1 with prior rupture of the biceps tendon and bunching of the biceps with flexion. Patient 2 with acute rupture of the biceps tendon in the left arm; the tendon rupture occurred with trivial trauma, five years after Cardiac Amyloidosis diagnosis.

2. ATTRwt may contribute to heart failure. Wild-type transthyretin amyloidosis (ATTRwt) is increasingly recognized as an important cause of heart failure with preserved ejection fraction (HFpEF).

WHY IS IT IMPORTANT?

Bicep bunching may be a marker of wild-type transthyretin (TTR) cardiac amyloidosis, potentially giving physicians an easy way to determine the underlying cause of heart failure with preserved ejection fraction (HFpEF) in some patients. Those who were aware, reported that the distal biceps tendon ruptured approximately five years prior to heart failure diagnosis, thus perhaps offering a leading insight.

In addition, early diagnosis of wild-type TTR cardiac amyloidosis (ATTRwt) is important because treatments are now available to slow, if not halt, disease progression. Unfortunately, the diagnosis of ATTRwt is often not considered in bicep bunching cases due to the perceived rarity of the disease.

“The clinical importance [of this study] is that the detection of a ruptured distal biceps tendon may be a clue for the diagnosis of wild-type TTR amyloidosis as the cause for heart failure. This diagnosis is often overlooked in clinical practice, so this relatively simple evaluation could increase detection of the disease,” said Stuart Katz, MD, of NYU Langone Health. “Enhanced detection could lead to better treatment.”

EXPERT INSIGHTS VIDEO ON MUSCULOSKELETAL MANIFESTATIONS

Dr. Shari Liberman, a hand and upper extremities surgeon from Houston Methodist Orthopedics & Sports Medicine, discussed six orthopedic manifestations and their pathology as it relates to systemic amyloidosis. Published studies, coupled with her experience, has led to a belief that these manifestations can offer important evidence of amyloidosis. She concludes with thoughts regarding an orthopedic differential and biopsy considerations for each of these manifestations.

Sources ———————————————————————————————————————

https://www.healthline.com/health/popeye-deformity

https://www.medpagetoday.com/cardiology/chf/67850

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5818850/

https://www.researchgate.net/publication/319657750_Association_Between_Ruptured_Distal_Biceps_Tendon_and_Wild-Type_Transthyretin_Cardiac_Amyloidosis

https://www.shoulderdoc.co.uk/article/721

https://www.thelancet.com/doi/story/10.1016/vid.2019.02.26.107679

https://www.youtube.com/watch?v=fHXu_0IZ3vU

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 HERE.

Thank you.

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Source:

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.

https://www.jacc.org/doi/10.1016/j.jacc.2022.11.022

Historically it has been thought that the majority of elderly cardiomyopathy patients diagnosed with amyloidosis, ATTR-CM, transthyretin amyloid cardiomyopathy, suffered from wild-type, a non-genetic version of the disease that most commonly affects but is not exclusive to men over seventy years of age. A study in the UK conducted from January 2010 through August 2022 was conducted to determine whether this was true. It is thought that this study was the first time such a large population of ATTR-CM patients was studied to consider the actual prevalence of the differing disease types. The researchers stated purpose was “ …to estimate the prevalence, clinical characteristics and prognostic implications of transthyretin (TTR) variants among elderly patients diagnosed with ATTR-CM.”¹

A paper detailing the results of the study, ‘Prevalence, characteristics and outcomes of older patients with hereditary versus wild-type transthyretin amyloid cardiomyopathy’ by A. Porcari et al.¹, published January 16, 2023 in the European Journal of Heart Failure provide specifics about the methodology, statistical analysis of the results, and an analysis of the findings. An invited editorial about that article, ‘Variant and wild type transthyretin amyloidosis: two sides of the same coin or different currencies in different pockets?’, by Osnat Itzhaki Ben Zadok and Rodney H. Falk provides comments and an assessment of the study discussed in the A. Porcari paper.² A helpful summary of the differences between wild-type and hereditary amyloidosis can be found here.³

With increased awareness of amyloidosis and the various types as well as developments in the technology used to diagnose and type ATTR amyloidosis, it has now become relatively easy to determine whether a patient is suffering from the hereditary version or the wild-type. Imaging has become preferred over the previous “gold standard” of endomyocardial biopsy. The study population was selected from those for whom ATTR-CM was established as the diagnosis using echocardiography, nuclear scintigraphy, and TTR gene sequencing at the National Amyloidosis Center (NAC) in London, the single center for diagnosing and treating amyloidosis patients in the UK. Correct diagnosis and typing of the disease could allow for appropriate treatment to begin resulting in the likelihood of an improved disease management and outcome for the patient.

A total of 2,029 patients were accepted into the study, none of whom had previously received genetic testing for the disease. Patients identified through gene sequencing as having the hereditary version of the disease, 141 total, were moved to medication as soon as it became available. Of note, all patients who had been treated with any of the then available medication for ATTR amyloidosis — tafamidis, inotersen, diflunisal, or patisiran, and all patients who were participating in clinical trials for therapies for the disease — were excluded from the study. This was to remove the possibility of the therapies skewing the results. All participants were 70 years of age or older. The patients were all followed at the NAC in London, the only center for the diagnosis and treatment of Amyloidosis in the UK. This allowed for unprecedented access to what is thought to be the majority of ATTR-CM in the country. All causes of death were tracked for the duration of the study.

The table below illustrates the number of ATTM-CM patients in the study who were thought to be suffering from wild-type amyloidosis but after testing were actually found to have a hereditary, variant, version of the disease instead. Specific data from the tests used to make this determination can be found in the article where the following table is found.

Correcting the diagnosis then allowed the patients to be moved to more appropriate therapies.

Further discussion in the Porcari article considers the study population and those currently listed in the THAOS registry⁴ by percentage of total ATTR-CM patients in the United Kingdom, the United States, and the rest of the World for both wild-type and variant disease with the more common variants also identified. It is thought that as many as 20% of ATTR-CM identified as having the wild-type disease likely have a variant version but have not had genetic testing to correctly determine that.¹

The article goes on to discuss the most commonly seen demographics and presentations of ATTRwt-CM and ATTRv-CM in the elderly, and the effects of the various therapies currently available as well as their mechanisms and limitations.

While some symptoms of wild-type amyloidosis and hereditary, variant, amyloidosis are similar, it is easy to differentiate between the two diseases. With careful testing, as noted in the article, this then allows for the proper management and treatment of the disease. The concluding paragraph of the paper really sums up the findings and sends an important message.

“In conclusion, up to 20.7% of elderly patients with ATTR-CM carry a pathogenic TTR mutation with a higher proportion still among specific ethnic groups. Among patients diagnosed with ATTR-CM, younger age at diagnosis, female gender, Afro-Caribbean ethnicity, AF, IHD, polyneuropathy and orthostatic hypotension are independently associated with ATTRv-CM. A diagnosis of ATTR-CM should prompt sequencing of the TTR gene in all patients, regardless of age, gender and ethnicity.”¹

Sources:
1. https://onlinelibrary.wiley.com/doi/full/10.1002/ejhf.2776 Prevalence, characteristics and outcomes of older patients with hereditary versus wild-type transthyretin amyloid cardiomyopathy, Aldostefano Porcari, Yousuf Razvi, Ambra Masi, Rishi Patel, Adam Ioannou, Muhammad U. Rauf, David F. Hutt, Dorota Rowczenio, Janet Gilbertson, Ana Martinez-Naharro, Lucia Venneri, Carol Whelan, Helen Lachmann, Ashutosh Wechalekar, Candida Cristina Quarta, Marco Merlo, Gianfranco Sinagra, Philip N. Hawkins, Marianna Fontana, Julian D. Gillmore, January 2023

2. https://onlinelibrary.wiley.com/doi/10.1002/ejhf.2808 Variant and wild type transthyretin amyloidosis: two sides of the same coin or different currencies in different pockets?
Osnat Itzhaki Ben Zadok, Rodney H. Falk, February 2023

3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7500251/ Transthyretin Amyloidosis: Update on the Clinical Spectrum, Pathogenesis, and Disease-Modifying Therapies
Haruki Koike and Masahisa Katsuno, September 2020

4. https://www.jns-journal.com/article/S0022-510X(15)00745-5/fulltext THAOS – The Transthyretin Amyloidosis Outcome Survey , F. Barroso, M. Waddinton-Cruz, et. Al., October 2015

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.

SIGNIFICANTLY UNDER-DIAGNOSED

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.

https://rarediseases.org/rare-diseases/amyloidosis/

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.

doi: 10.1001/jama.2019.17935.

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

https://pubmed.ncbi.nlm.nih.gov/35377943/

SUMMARY

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:

Worldwide Hotspots of Hereditary TTR Amyloidosis (ATTRv)

Hereditary Amyloidosis: T60A Variant

Header

Slider

Symptoms

Types of Neuropathy

Amyloidosis

Neurological Complications of ATTR Amyloidosis

Risk Factors

Types of Cardiomyopathy

Amyloidosis

Expert Insights – Cardiac Clues and Clinical Signs

WHAT IS IT?

WHAT DOES IT POTENTIALLY INDICATE?

WHY IS IT IMPORTANT?

EXPERT INSIGHTS VIDEO ON MUSCULOSKELETAL MANIFESTATIONS

Sources ———————————————————————————————————————

Patient Case #1

Patient Case #2

Once Diagnosed, Next is a Treatment Plan

CLICK HERE to read/download ASNC’s Guide for Understanding Amyloidosis

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Source:

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

SIGNIFICANTLY UNDER-DIAGNOSED

SUMMARY

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