Neuropathy Assessment and Treatment Patterns in Patients With Hereditary Transthyretin Amyloidosis: A Single-Center Analysis of Stabilizer and Gene Silencer Utilization

In a single-center study of a predominantly V142I hereditary transthyretin amyloidosis cohort with high cardiac involvement, stabilizer use was nearly universal among eligible patients while gene silencer utilization was significantly associated with documented objective neuropathy and non-cardiac phenotypes, highlighting the need for systematic neurological assessment even when cardiac disease predominates.

The Gist

Imagine your body is a bustling city, and the Transthyretin (TTR) protein is a delivery truck that normally carries vitamins and hormones to different neighborhoods. In a condition called Hereditary Transthyretin Amyloidosis (hATTR), these trucks break down. Instead of delivering their cargo, they spill a sticky, gooey substance called "amyloid" all over the streets. Over time, this goo piles up like trash, clogging the roads and damaging the city's infrastructure.

This study looks at a specific group of people in this city who have a genetic "glitch" (the V142I variant). This glitch is very common in people of African American descent.

Here is the breakdown of the study using simple analogies:

1. The Two Main Neighborhoods: The Heart and The Nerves

Usually, when this "sticky goo" piles up, it hits two main areas:

• The Heart (The Power Plant): The goo clogs the heart, making it hard to pump blood. This is the most common problem for people with this specific genetic glitch.
• The Nerves (The Electrical Grid): The goo coats the wires (nerves) that send signals to your hands, feet, and organs. This causes numbness, tingling, or pain.

The Big Surprise: For a long time, doctors thought this specific genetic glitch only clogged the Power Plant (the heart). They thought the Electrical Grid (nerves) was safe. This study says, "Wait a minute! The grid is getting clogged too, and we might be missing it."

2. The Study: A Detective's Review

The researchers went back through the medical records of 54 patients at a big hospital. They were like detectives looking for clues about how much "sticky goo" was in the heart versus the nerves.

• The Heart Findings: As expected, almost everyone (94%) had clogged power plants (heart disease).
• The Nerve Findings: They found that more than half of these patients (55%) also had signs of clogged wires (neuropathy).
  • Some had hard proof (like a mechanic testing the wires with a multimeter—this is called an EMG test).
  • Some had suspicion (the patient complained of tingling, but no test was done).
  • Some had no clue (the records were messy).

3. The Treatments: Two Different Tools

Doctors have two main ways to fix this problem:

• The Stabilizers (The Glue): These drugs (like tafamidis) act like super-glue. They hold the broken delivery trucks together so they don't fall apart and spill the goo in the first place.

  • Result: Since almost everyone had heart trouble, doctors used this "glue" on almost everyone who needed it (95% of eligible patients). This is working well!

• The Gene Silencers (The Mute Button): These drugs (like patisiran) act like a mute button on the factory making the broken trucks. They stop the body from making the bad trucks entirely.

  • Result: These are very powerful for fixing the clogged wires (nerves). However, the study found they were only used when there was clear proof of nerve damage.
  • The Problem: If a patient had heart trouble and some nerve symptoms, but hadn't gotten the "multimeter test" (EMG) yet, they often didn't get the "Mute Button" drug. The doctors were waiting for 100% proof before pulling the trigger.

4. The "Non-Cardiac" Group

There were three patients who didn't have heart trouble, only nerve trouble.

• They didn't get the "Glue" (Stabilizer) because their power plant was fine.
• They did get the "Mute Button" (Gene Silencer) because their wires were clogged.
• This shows that the treatment depends entirely on where the damage is.

5. The Main Lesson: Don't Ignore the Wires

The authors are saying: "Just because the heart is the main problem, don't ignore the nerves."

Because the "Mute Button" drugs are so good at fixing nerve damage, we need to check the wires in every patient, even if their heart is the one screaming for help.

• The Analogy: Imagine a house where the furnace is on fire (Heart). You rush to put out the fire. But if you don't check the smoke detectors in the hallway (Nerves), you might miss a second fire starting there.
• The Takeaway: The study suggests that doctors should be more aggressive about testing for nerve damage (using those "multimeter" tests) so they can prescribe the powerful "Mute Button" drugs sooner, rather than waiting for the symptoms to become undeniable.

Summary in One Sentence

This study found that while this genetic disease mostly hurts the heart, it also quietly damages the nerves in over half the patients, and we need to be better at checking for that nerve damage so we can give patients the best possible medicine before it's too late.

Technical Summary

1. Problem Statement

Hereditary transthyretin amyloidosis (hATTR) is a systemic disease caused by TTR gene mutations, leading to amyloid fibril deposition. The V142I variant is the most common pathogenic mutation, affecting approximately 3–4% of African Americans. Historically, this variant has been characterized as cardiac-predominant, with neurological involvement often considered rare or underrecognized.

However, emerging data suggests polyneuropathy may be more prevalent in V142I carriers than previously thought. A critical gap exists in understanding:

• The true prevalence of neuropathy in V142I-predominant cohorts when using varying diagnostic criteria (from administrative coding to formal neurophysiologic testing).
• How neurological documentation influences treatment selection, specifically the utilization of gene silencer therapies (patisiran, vutrisiran, eplontersen), which historically required a neuropathy indication, versus TTR stabilizers (tafamidis, acoramidis, diflunisal).
• Whether systematic neurological assessment is necessary even in patients with dominant cardiac phenotypes.

2. Methodology

• Study Design: Retrospective single-center cohort study conducted at a major academic medical center (Georgetown University/MedStar Health).
• Population: 54 patients diagnosed with hATTR between 2017 and 2025.
  • Inclusion: Confirmed pathogenic TTR variant via genetic testing; documented amyloidosis and/or neuropathy via ICD-10 coding.
  • Exclusion: Unknown genotype, hospice/comfort care only, pre-symptomatic carriers without clinical manifestations.
• Data Collection: Review of electronic medical records for demographics, TTR variants, cardiac involvement (echocardiography, MRI, PYP scan), neurological assessments (consults, EMG/NCS), and treatment history.
• Neuropathy Classification: Patients were categorized into four mutually exclusive groups based on documentation quality:
  1. With ancillary testing: Abnormal EMG/Nerve Conduction Study (NCS).
  2. Without ancillary testing: Clinical documentation of neuropathy by a provider without confirmatory testing.
  3. Symptoms only: Patient-reported symptoms (numbness, pain) without exam findings or formal evaluation.
  4. Unclear: Insufficient documentation.
• Treatment Assessment: Utilization of TTR stabilizers and gene silencers was analyzed. Notably, no patients in this cohort received gene silencers under the cardiomyopathy indication (FDA approved March 2025); all gene silencer use was predicated on the polyneuropathy indication.
• Confounding Factors: Conditions such as diabetes, CKD, alcohol use, and B12 deficiency were documented to contextualize neuropathy findings.

3. Key Results

• Demographics & Phenotype:
  • 88.9% of patients were African American; 85.2% carried the V142I variant.
  • 94.4% (51/54) had confirmed cardiac involvement, consistent with the cardiac-predominant phenotype.
• Neuropathy Prevalence:
  • 55.6% (30/54) had confirmed or suspected neuropathy based on clinical documentation.
  • Breakdown: 31.5% (17/54) had EMG confirmation; 24.1% (13/54) had clinical documentation without EMG; 18.5% (10/54) had symptoms only.
  • EMG completion rate was limited overall (57.4% among those with suspected neuropathy).
• Treatment Patterns:
  • Stabilizers: Among eligible cardiac patients, 95.2% (40/42) received stabilizers.
  • Gene Silencers: Overall utilization was 29.6% (16/54).
    • Correlation with Documentation: Gene silencer use was highest in patients with ancillary testing confirmation (47.1%), intermediate in those with clinical documentation (30.8%), and lowest in those with symptoms only (10.0%).
    • Concurrent Therapy: 13 of 16 patients on gene silencers were also on stabilizers, indicating an additive treatment strategy.
  • Non-Cardiac Phenotype: The 3 patients without confirmed cardiac disease (1 V142I, 1 V50M, 1 P84L) all received gene silencers (100%) and no stabilizers.
• Impact of Confounders: Treatment patterns were similar regardless of the presence of confounding conditions (e.g., diabetes), suggesting amyloidosis was the primary driver for treatment decisions.

4. Key Contributions

• Challenging the "Cardiac-Only" Dogma: The study provides evidence that over half of a V142I-predominant cohort has documented neuropathy, challenging the historical view that this variant causes exclusively cardiac disease.
• Diagnostic Methodology Matters: The paper highlights a massive disparity in reported neuropathy prevalence based on diagnostic rigor. While administrative coding might suggest low prevalence, the study found 31.5% with objective EMG confirmation and 55.6% with any clinical evidence. This suggests neuropathy is significantly underdiagnosed when relying solely on coding or lack of formal testing.
• Treatment Access Barriers: The study demonstrates that gene silencer utilization is tightly coupled with the documentation of neuropathy. As new indications for gene silencers in cardiomyopathy emerge (post-March 2025), there is a risk that neuropathy will go unassessed because it is no longer a prerequisite for prescribing, potentially missing opportunities for multidisciplinary management.
• Additive Therapy Model: The data supports a clinical pattern where gene silencers are layered onto stabilizer therapy rather than replacing them, particularly in patients with mixed phenotypes.

5. Significance and Implications

• Clinical Practice: The findings strongly support systematic neurological assessment (including EMG/NCS) for all hATTR patients, even those with dominant cardiac phenotypes. Relying on symptoms alone or administrative codes underestimates disease burden.
• Therapeutic Strategy: As the therapeutic landscape evolves (e.g., gene silencers approved for cardiac indications), clinicians must remain vigilant to ensure neuropathy is characterized. This is crucial for:
  • Establishing baseline severity.
  • Guiding monitoring protocols.
  • Identifying patients who may benefit from specific multidisciplinary care.
• Future Research: The authors call for standardized neuropathy assessment criteria in hATTR to resolve the wide variation in prevalence rates (2–9% in population studies vs. >90% in specialized centers). They suggest future directions including serum biomarkers (Neurofilament Light Chain) and nerve ultrasound to improve detection sensitivity beyond conventional EMG.

Conclusion: In a predominantly V142I cohort, while cardiac disease is the primary manifestation, neuropathy is highly prevalent but often under-confirmed by objective testing. Treatment patterns reveal that gene silencer access is currently driven by neuropathy documentation, underscoring the need for rigorous neurological evaluation to optimize patient management and therapeutic selection.