Amyloid disease, formally called amyloidosis, is a group of conditions in which abnormally folded proteins build up in organs and tissues, gradually interfering with their ability to function. These protein deposits, called amyloid fibrils, are tough, insoluble, and resist the body’s normal cleanup mechanisms. The disease can affect the heart, kidneys, liver, nerves, and digestive tract, sometimes several at once. It is uncommon but increasingly recognized, with the most frequently diagnosed form (light-chain amyloidosis) affecting roughly 17 out of every million adults per year in the United States.
How Amyloid Proteins Form
Every protein in your body needs to fold into a precise three-dimensional shape to do its job. When something disrupts that folding process, whether a genetic mutation, a shift in the body’s chemistry, or overproduction of a particular protein, the result is a misshapen molecule. Normally, cellular quality-control systems catch and recycle these defective proteins. In amyloidosis, the system is overwhelmed or the misfolded proteins are unusually resistant to cleanup.
The misfolded proteins clump together into long, thread-like fibers called amyloid fibrils. A key feature of these fibrils is that they expose sticky, water-repelling surfaces that were supposed to stay buried inside the protein’s core. Those surfaces latch onto each other, forming dense, insoluble deposits that wedge themselves between cells in organs and tissues. Over time, these deposits physically crowd out healthy tissue and disrupt organ function.
The Main Types of Amyloidosis
There are several forms of amyloidosis, each named for the specific protein that misfolds. The three most clinically important types affect different people for different reasons.
AL (Light-Chain) Amyloidosis
This is the most commonly diagnosed systemic form. It starts in the bone marrow, where abnormal plasma cells produce excess fragments of antibodies called light chains. These light chains misfold and deposit throughout the body. AL amyloidosis often affects the heart, kidneys, liver, and nerves. It is closely related to certain blood cancers, though it is not itself a cancer in the traditional sense.
ATTR (Transthyretin) Amyloidosis
In this form, a protein called transthyretin, which normally carries thyroid hormone and vitamin A in the blood, becomes unstable and misfolds. There are two versions. The hereditary form results from a genetic mutation in the transthyretin gene and can appear as early as the 30s or 40s. The wild-type form has no genetic mutation; the protein simply becomes unstable with age. Wild-type ATTR primarily affects the heart and is increasingly found in older adults, particularly men over 70. Many experts believe it has been significantly underdiagnosed for decades.
AA (Secondary) Amyloidosis
AA amyloidosis is triggered by prolonged inflammation. The liver produces an inflammatory protein called serum amyloid A during chronic illness, and years of overproduction can lead to amyloid deposits, most commonly in the kidneys and liver. In industrialized countries, rheumatoid arthritis is the leading trigger, accounting for 23 to 51 percent of AA cases. Juvenile idiopathic arthritis and ankylosing spondylitis are also significant contributors. In developing countries, chronic infections like tuberculosis, leprosy, and long-standing bone infections are more common causes.
Symptoms and Organ Involvement
Amyloidosis is notoriously difficult to recognize early because its symptoms mimic many other conditions. The kidneys and heart are the most commonly affected organs, followed by the nervous system, lungs, and liver. What you experience depends entirely on where the amyloid builds up.
When amyloid infiltrates the heart, it stiffens the heart muscle and reduces its ability to fill with blood between beats. Less blood gets pumped with each contraction, causing shortness of breath, fatigue, and fluid retention, particularly swelling in the ankles and legs. If the electrical system is affected, irregular heart rhythms can develop. Cardiac involvement is the most dangerous complication and the primary driver of poor outcomes in AL amyloidosis.
In the kidneys, amyloid damages the filtering system. Early signs often include protein leaking into urine and progressive swelling in the legs. Without treatment, kidney function can decline to the point of failure. Nerve involvement tends to show up as numbness, tingling, or pain in the hands and feet. Damage to the nerves controlling involuntary body functions can cause dizziness when standing up quickly, alternating bouts of constipation and diarrhea, or a persistent drop in blood pressure.
Some symptoms are more distinctive. An enlarged tongue with a rippled or scalloped edge is a hallmark of AL amyloidosis, though it doesn’t occur in every case. Easy bruising, purplish patches around the eyes, unexplained weight loss, and severe fatigue that seems disproportionate to any identifiable cause are all red flags that should prompt further investigation.
How Amyloidosis Is Diagnosed
A definitive diagnosis requires a tissue biopsy. A small sample of tissue is taken, most commonly from abdominal fat just beneath the skin, which is a relatively simple and low-risk procedure. Samples can also be collected from the kidney, rectum, gum tissue, or bone marrow. The tissue is stained with a dye called Congo red. Under normal light, amyloid deposits appear salmon-pink. Under polarized light, they produce a distinctive apple-green glow, a finding that is considered unmistakable confirmation of amyloid.
Once amyloid is confirmed, the next step is identifying which protein is involved, because treatment differs dramatically between types. Blood and urine tests can detect abnormal light chains (pointing to AL), while genetic testing can reveal transthyretin mutations (pointing to hereditary ATTR).
For suspected cardiac ATTR amyloidosis specifically, a nuclear imaging scan using a radioactive tracer can often confirm the diagnosis without a heart biopsy. The tracer is absorbed by amyloid deposits in the heart muscle, and strong uptake on the scan, combined with the absence of abnormal light chains in blood tests, is considered diagnostic. This non-invasive approach has transformed how cardiac ATTR is identified and is a major reason detection rates have climbed in recent years.
Treatment by Type
There is no single treatment for amyloidosis. The strategy depends on which protein is causing the problem and which organs are involved.
Treating AL Amyloidosis
Because the abnormal proteins originate from rogue bone marrow cells, treatment borrows heavily from blood cancer therapy. The goal is to eliminate or suppress the cells producing the misfolded light chains. Most patients receive chemotherapy combinations that target plasma cells, and the backbone of initial treatment is typically a drug that blocks the cellular recycling machinery these cells depend on to survive, often combined with a steroid to enhance the effect.
For patients who are young and healthy enough, an autologous stem cell transplant is one of the most effective options. Your own stem cells are collected, high-dose chemotherapy wipes out the abnormal marrow cells, and the stored stem cells are infused back to rebuild the bone marrow. This approach produces deep, durable responses in many patients, but the procedure carries real risks, and candidates need to be carefully selected. Newer antibody-based therapies that directly target plasma cells are also increasingly used and have expanded treatment options for patients who aren’t transplant candidates.
Treating ATTR Amyloidosis
ATTR treatment has advanced rapidly in the past several years. Two main strategies exist. The first uses oral medications called stabilizers, which bind to the transthyretin protein and prevent it from falling apart and misfolding. These drugs have been shown to significantly reduce the combined risk of death and hospitalization in patients with cardiac ATTR amyloidosis.
The second approach uses gene-silencing therapies that reduce the liver’s production of transthyretin altogether. One such therapy is administered as a single injection under the skin once every three months. By dramatically lowering the amount of circulating transthyretin, these treatments reduce the raw material available to form new amyloid deposits. Clinical trials have confirmed that this approach improves outcomes in cardiac amyloidosis, and the convenience of infrequent dosing is a practical advantage for patients.
Treating AA Amyloidosis
The most effective strategy for AA amyloidosis is controlling the underlying inflammatory disease that drives it. When inflammation is brought under control, the liver stops overproducing the precursor protein, and existing amyloid deposits can sometimes stabilize or even slowly regress. This means aggressive management of rheumatoid arthritis, treatment of chronic infections, or control of whatever inflammatory condition is fueling the process.
Outlook and Survival
Prognosis varies enormously depending on the type of amyloidosis, which organs are involved, and how early the disease is caught. For AL amyloidosis, the overall median survival is approximately five years, but this number conceals a wide range. Patients diagnosed at the earliest stage, before significant heart damage, have a median survival exceeding ten years. Those with advanced cardiac involvement at diagnosis face a much shorter timeline, sometimes measured in months.
More than 40 percent of AL patients die within the first year of diagnosis, a statistic that reflects how often the disease is caught late, after substantial organ damage has already occurred. This underscores why earlier recognition matters. The symptoms are vague, mimicking heart failure, kidney disease, or neuropathy, so amyloidosis often isn’t considered until standard treatments for those conditions fail.
ATTR amyloidosis, particularly the wild-type form affecting the heart, generally progresses more slowly than AL. With the arrival of stabilizer and gene-silencing therapies, the outlook for ATTR patients has improved substantially compared to even a decade ago. AA amyloidosis outcomes depend largely on whether the underlying inflammatory condition can be controlled; when it can, the prognosis is often favorable.