Amyloidosis is a group of diseases in which abnormally folded proteins build up in your organs and tissues, gradually interfering with how they work. These misfolded proteins clump together into stiff, insoluble fibers called amyloid fibrils that deposit outside of cells, and the body has no effective way to clear them. Over time, the buildup can damage the heart, kidneys, liver, nerves, and other organs. It’s relatively rare: in the United States, the most common form (called AL amyloidosis) affects roughly 17 per million adults each year.
How Proteins Misfold and Build Up
Your body produces thousands of different proteins, and normally they fold into precise three-dimensional shapes that allow them to function. In amyloidosis, certain proteins lose their stable structure and refold into an abnormal shape that makes them sticky. These misshapen proteins latch onto each other, forming long, rigid fibers that settle into the spaces between cells in organs and tissues.
At least 21 different proteins have been identified as capable of forming amyloid deposits. Several factors can push a protein toward this abnormal state: aging naturally destabilizes some proteins, genetic mutations can make a protein structurally fragile from birth, and chronic inflammation can flood the bloodstream with proteins at concentrations high enough to trigger clumping. Even environmental conditions like changes in acidity, temperature, or the presence of certain metal ions can tip the balance toward misfolding.
Once amyloid fibrils start forming, the process tends to accelerate. The fibrils are extremely resistant to the body’s normal cleanup mechanisms, so deposits grow over months and years, progressively crowding out healthy tissue and disrupting organ function.
The Three Major Types
AL Amyloidosis (Light Chain)
AL amyloidosis is the most commonly diagnosed form. It starts in the bone marrow, where abnormal plasma cells produce excess fragments of antibodies called light chains. These light chain proteins misfold and deposit as amyloid in virtually any organ. The heart, kidneys, liver, and nerves are the most frequent targets. Some people develop an enlarged tongue, which is a hallmark sign. AL amyloidosis sometimes occurs alongside blood cancers like multiple myeloma or lymphoma, though it often appears on its own.
AA Amyloidosis (Inflammatory)
AA amyloidosis develops as a complication of long-standing infection or inflammatory disease. Conditions like rheumatoid arthritis, familial Mediterranean fever, chronic bone infections, and inflammatory bowel disease cause the liver to continuously produce an inflammatory protein called SAA. Over time, fragments of SAA accumulate as amyloid, most often in the kidneys. The first sign is usually protein leaking into the urine.
ATTR Amyloidosis (Transthyretin)
ATTR amyloidosis involves a protein called transthyretin (TTR), which normally carries thyroid hormone and vitamin A in the blood. It comes in two forms. In the hereditary form, a genetic mutation makes the TTR protein unstable so it breaks apart and refolds into amyloid fibrils. In wild-type ATTR, the TTR gene is completely normal, but the protein gradually destabilizes with age, typically causing heart problems in men over 60. Both forms primarily affect the heart and peripheral nerves.
The most common hereditary mutation, called Val50Met, clusters in families of Portuguese, Swedish, and Japanese descent. Another variant, Val142Ile, is carried by 3 to 4 percent of African Americans. Most people with this variant eventually develop heart-related amyloidosis later in life, making it a significant and underrecognized cause of heart failure in Black communities.
Symptoms by Organ
Amyloidosis is notoriously difficult to recognize because its symptoms mimic many other conditions and depend entirely on where amyloid deposits accumulate. Most people have involvement in more than one organ by the time they’re diagnosed.
When the heart is affected, amyloid stiffens the heart walls, making it harder for the heart to fill and pump blood. This leads to shortness of breath, swelling in the legs and ankles, fatigue, and irregular heartbeats. Cardiac involvement is the most dangerous complication and the primary driver of prognosis.
Kidney involvement typically shows up first as protein spilling into the urine, which can progress to significant fluid retention and eventually kidney failure. Nerve damage causes numbness, tingling, or burning pain in the hands and feet, often starting in the fingers and toes and working inward. Some people experience digestive problems like early fullness, nausea, diarrhea, or unintentional weight loss when amyloid affects the gut or its nerve supply. An enlarged tongue, purplish patches around the eyes, and easy bruising are distinctive signs that point specifically toward AL amyloidosis.
How Amyloidosis Is Diagnosed
Diagnosis requires a tissue biopsy that confirms the presence of amyloid deposits. The standard first step is a fat pad aspirate, where a small sample of abdominal fat is taken with a needle. This simple procedure detects amyloid in about 80 percent of cases. If negative, a biopsy of the affected organ (heart, kidney, or liver) provides a definitive answer.
The tissue sample is stained with a dye called Congo red. Amyloid absorbs this dye and produces a distinctive apple-green glow when viewed under polarized light. This remains one of the essential diagnostic criteria.
Confirming the type of amyloidosis is just as important as detecting it, because treatments differ dramatically. Mass spectrometry, which identifies the exact protein making up the amyloid fibrils, is now considered the standard method for typing. Getting the type wrong can lead to entirely inappropriate treatment, so specialized centers often re-examine biopsy samples with this technology even if a type has already been suggested by other tests.
For suspected ATTR amyloidosis affecting the heart, a nuclear bone scan can detect cardiac amyloid deposits without a heart biopsy in many cases, significantly simplifying diagnosis.
Prognosis and Staging
Survival varies enormously depending on the type of amyloidosis, which organs are involved, and how early it’s caught. Heart involvement is the single most important factor in determining outcomes, particularly in AL amyloidosis.
AL amyloidosis is staged primarily using blood markers of heart stress and damage. Patients diagnosed at the earliest stage, before the heart is significantly affected, have a median survival of roughly 11 to 12 years. At intermediate stages, that drops to 5 to 8 years. When the heart is heavily involved at diagnosis, median survival can be as short as 5 to 6 months. These numbers underscore why early detection matters so much: catching the disease before it damages the heart transforms the outlook from dire to manageable.
ATTR amyloidosis, particularly the wild-type form, generally progresses more slowly than AL amyloidosis. Many patients live years to decades after diagnosis, especially with newer therapies now available.
Treatment for AL Amyloidosis
Because AL amyloidosis originates from abnormal cells in the bone marrow, treatment targets those cells using chemotherapy combinations similar to those used in blood cancers. The goal is to rapidly and deeply reduce the production of the misfolded light chain proteins, giving organs a chance to recover.
The standard first-line regimen combines three drugs (a proteasome inhibitor, an alkylating agent, and a steroid) and is often enhanced with a fourth drug, a targeted antibody that attacks the abnormal plasma cells directly. Clinical trials showed this four-drug combination produces faster and deeper responses. For eligible patients, a stem cell transplant may follow initial chemotherapy to consolidate the response. Treatment success is measured by how completely the abnormal light chains disappear from the blood, because organs can only begin healing once the supply of amyloid-forming protein is shut off.
Treatment for ATTR Amyloidosis
ATTR amyloidosis treatment has been transformed in recent years. Two main strategies now exist: stabilizing the TTR protein so it doesn’t break apart, and silencing its production entirely.
TTR stabilizers work by binding to the transthyretin protein and holding it in its normal four-part structure, preventing it from disassembling into the individual pieces that misfold. In clinical trials, tafamidis (the first approved stabilizer) reduced the combined risk of death and cardiovascular hospitalization by about 31 percent over 30 months, while also preserving patients’ ability to walk and their quality of life. A newer stabilizer, acoramidis, works through a similar mechanism.
TTR silencers take a different approach: they block the liver from making the transthyretin protein at all. Vutrisiran, given as a subcutaneous injection once every three months, significantly reduced deaths and cardiovascular events in clinical trials. Some patients now receive both a stabilizer and a silencer together, though research is still clarifying which combinations work best for whom.
The 2025 guidance from the American College of Cardiology emphasizes starting disease-modifying therapy early, even before symptoms become severe, rather than waiting for clear-cut heart failure.
Genetic Testing for Families
When hereditary ATTR amyloidosis is diagnosed in one family member, genetic testing is recommended for adult blood relatives. The goal is to identify carriers of the TTR mutation before symptoms develop, since early treatment can slow or prevent organ damage. Once the specific mutation in a family is known, testing is straightforward: a blood sample is all that’s needed.
Testing asymptomatic children is generally not recommended, since symptoms typically don’t appear until adulthood and early testing in minors removes their ability to make that choice themselves. For adults who test positive, regular monitoring with heart imaging and nerve function assessments allows doctors to start treatment at the first signs of disease rather than after significant damage has already occurred.