What Are the Risks of Misdiagnosing ATTR vs AL Amyloidosis?

Safety Warning: Do not stop or delay any prescribed treatment based on this information. AL amyloidosis can progress rapidly, and treatment is often urgent. If you are unsure about your diagnosis, urgently ask your medical team to explain how your amyloidosis was typed, or seek a second opinion from an amyloidosis center.

If you have ATTR amyloidosis but are mistakenly treated for AL amyloidosis, you may receive therapies directed at bone marrow cells, which do not treat ATTR deposits ^[1]. This exposes you to chemotherapy side effects unnecessarily and delays the specific medications that can slow ATTR progression ^[2]. Accurate “typing” (identifying the exact protein causing the disease) is essential before finalizing a treatment plan ^[3].

Different Diseases, Different Treatments

Although AL and ATTR amyloidosis both involve abnormal proteins building up in your organs, they are driven by different precursor proteins and require completely different treatments ^[4][5].

• AL amyloidosis is a disease of the bone marrow. It is caused by an abnormal clone of plasma cells producing toxic “light chain” proteins ^[4]. The treatment involves chemotherapy or immunotherapy designed to suppress these plasma cells ^[1].
• ATTR amyloidosis involves transthyretin (TTR), a protein primarily produced by the liver ^[5]. TTR can become unstable due to aging (wild-type ATTR) or a genetic variant (hereditary ATTR) ^[6].

Because AL chemotherapy targets plasma cells, it does not stop the liver from producing TTR or prevent ATTR amyloid from depositing in tissues ^[1][7].

The Risks of Incorrect Treatment

Chemotherapy regimens used for AL amyloidosis (which may include drugs like bortezomib and cyclophosphamide) are powerful and carry significant side effects. These can include lowered blood cell counts (which increase the risk of infection), severe fatigue, and nerve damage (peripheral neuropathy) ^[8][9].

For a patient with ATTR, these risks are compounded by their existing organ damage. ATTR frequently affects the heart, causing the muscle to become stiff (restrictive cardiomyopathy), leading to heart failure, dangerously low blood pressure, and irregular heartbeats ^[10][11].

• Heart Stress: Some AL treatments can place extra stress on the heart or cause fluid shifts that a stiff, amyloid-infiltrated heart struggles to handle ^[12][13].
• Transplant Risks: For eligible AL patients, stem cell transplants may be recommended. This involves high-dose chemotherapy and carries a high risk of early complications for patients with severe heart involvement ^[14][15].

The Cost of Lost Time

Time spent on the wrong treatment allows ATTR amyloidosis to progress. Today, there are targeted therapies for ATTR, including TTR stabilizers (which hold the protein together so it doesn’t form amyloid) and gene silencers (which substantially reduce the amount of TTR the liver produces) ^[7][16].

Research shows these disease-modifying treatments are most effective when started early, before irreversible organ damage occurs ^[2][17]. A misdiagnosis delays access to these therapies, allowing the heart and nerves to suffer potentially permanent damage ^[18].

How Misdiagnosis Happens (The MGUS Pitfall)

A common reason for misdiagnosis is the presence of an unrelated condition. Some people have a small, usually asymptomatic abnormal protein in their blood called MGUS (Monoclonal Gammopathy of Undetermined Significance).

If a doctor sees a monoclonal protein on a blood test and amyloid in the heart, they might assume it is AL amyloidosis ^[19][20]. However, ATTR can coexist with MGUS.

To prevent misdiagnosis, doctors use specific tests:

• Blood and Urine Tests: Serum free light chains, along with serum and urine immunofixation, are used to thoroughly check for monoclonal proteins.
• Bone Scans: A specialized cardiac bone scan can support a diagnosis of ATTR only if the blood and urine tests confirm there is absolutely no monoclonal protein present ^[20][21].
• Tissue Typing (Mass Spectrometry): If any monoclonal protein is found, or if a bone scan is not definitive, a tissue biopsy is required. The tissue is analyzed using mass spectrometry, which identifies the exact protein makeup of the amyloid deposits to confirm if it is AL or ATTR ^[3][22]. Once ATTR is confirmed, genetic testing is used to determine if it is the hereditary or wild-type form.

What to Bring to Your Appointment:
To ensure your diagnosis is clear, ask your doctor for copies of your:

• Biopsy pathology report (including the amyloid typing results)
• Serum free light chain and immunofixation lab results
• Cardiac bone scan report
• Echocardiogram or Cardiac MRI results
• Genetic testing results