AA Amyloidosis: What It Is, Why Inflammation Triggers It, and How Treatment Works

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026

This article is for general education only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your own health. Content is based on medically reviewed clinical sources last updated June 23, 2022, and current peer-reviewed literature.

TL;DR

AA amyloidosis is a rare complication of long-lasting inflammation in which misfolded serum amyloid A (SAA) protein clumps into deposits that damage organs, most often the kidneys. It develops in fewer than 5% of people with chronic inflammatory diseases and typically after many years of active inflammation. The cornerstone of treatment is controlling the underlying inflammatory condition, which lowers SAA levels and can halt or even reverse organ damage. Early diagnosis matters because untreated AA amyloidosis can be terminal, while well-managed disease can offer long survival.

Quick Answer: What Is AA Amyloidosis and How Is It Treated?

AA amyloidosis is a protein misfolding disorder in which the inflammatory protein serum amyloid A loses its normal shape, twists into rigid fibrils, and builds up as amyloid deposits in organs, primarily the kidneys, but also the liver, spleen, and digestive tract. It is a complication of chronic inflammatory conditions such as rheumatoid arthritis, inflammatory bowel disease, chronic infections, and inherited fever syndromes. Diagnosis requires a tissue biopsy with Congo red staining. Treatment targets the root cause: controlling the underlying inflammation to bring SAA protein levels down (ideally below 10 mg/L), which stops new deposits and can allow organs to recover. Early diagnosis and treatment is key.

What exactly is AA amyloidosis?

Amyloidosis is a group of rare disorders in which abnormal proteins lose their correct three-dimensional structure and become twisted, misshapen clumps called amyloid deposits. These deposits gather on tissues and organs and disrupt how they work. Doctors classify amyloidosis by the protein that misfolds, and AA amyloidosis is the type driven by the protein serum amyloid A (SAA), hence the name [1].

AA amyloidosis is also known as secondary amyloidosis, because it never occurs on its own. It is a complication of another ongoing disease process: long-term inflammation keeps SAA protein levels chronically elevated in the bloodstream, and over time the excess protein misfolds and accumulates [1] [2].

In plain terms: your body produces SAA as a normal emergency response to inflammation. When inflammation never switches off, the emergency protein is produced non-stop, gets stuck in its misfolded form, and gradually clogs up organs.

What causes AA amyloidosis?

AA amyloidosis happens when you have high levels of inflammation in your body over a long period, which boosts serum amyloid A protein levels in your bloodstream. Only a small share of people with chronic inflammatory diseases ever develop it, the deposits form in fewer than 5% of patients with chronic inflammatory disorders, which is why it is classified as a rare disease [1] [3].

SAA is an acute-phase protein made by the liver. Its production is switched on by inflammatory signals such as interleukin-1, interleukin-6, and tumor necrosis factor. During an acute inflammatory event, SAA can surge from a normal level below 5 mg/L to over 2,000 mg/L within 24 to 48 hours. In chronic inflammation, it stays persistently high, and that is the environment in which amyloid fibrils form [2] [4].

Class of underlying disease	Examples	Notes
Rheumatic / autoimmune diseases	Rheumatoid arthritis, juvenile idiopathic arthritis	Classic triggers in Western countries; AA develops in about 1 to 5% of patients with these conditions
Chronic bacterial infections	Chronic skin ulcers, osteomyelitis, bronchiectasis, tuberculosis	Still major drivers in some regions; declining in countries with strong antimicrobial access
Inflammatory bowel diseases	Crohn's disease, ulcerative colitis	Gut inflammation keeps SAA elevated for years
Inherited periodic fever syndromes	Familial Mediterranean fever (FMF), TRAPS	Lifelong autoinflammatory disease, comparatively higher individual risk
Blood cancers and others	Certain lymphomas, mesothelioma, Castleman disease	Less common associations
No identifiable cause	Idiopathic AA amyloidosis	About 25% of cases, the source of inflammation remains unclear

An important nuance for diagnosis: in nearly 25% of AA cases, no clear source of inflammation is ever found (idiopathic AA amyloidosis), and researchers have proposed that obesity may play a role in some of these cases [3]. And surprisingly, up to 10% of people with AA amyloidosis have no clinically obvious chronic inflammatory disease at all, which is one reason it can be missed or misdiagnosed as the more common AL amyloidosis [4].

Which organs does AA amyloidosis affect?

The kidney is the dominant target. In AA amyloidosis, the kidney is involved in virtually all patients, and renal disease drives the clinical picture. The most frequent presentation is protein leaking into urine (proteinuria), which can progress to nephrotic syndrome and then end-stage kidney failure. More than 90% of patients show proteinuria at presentation, and up to 10% already have kidney failure when the diagnosis is made [3] [5].

Beyond the kidneys, amyloid deposits also land on the liver and spleen (causing enlargement), the stomach and intestines (causing diarrhea and occasionally bleeding), and the adrenal glands. Heart involvement occurs but is rare, clinically significant cardiac disease appears in roughly 5% of cases and is usually mild when it does occur [3] [4].

Organ	How often involved	Typical effect
Kidneys	Nearly 100% (dominant organ)	Proteinuria, nephrotic syndrome, kidney failure
Liver	Frequent	Enlargement
Spleen	Frequent	Enlargement
Stomach and intestines	Common in advanced disease	Chronic diarrhea, occasional bleeding
Adrenal glands	Recognized site	Often subclinical
Heart	Rare (~5% clinically significant)	Usually mild

End-stage kidney failure accounts for the cause of death in an estimated 40 to 60% of AA amyloidosis cases, which makes the kidneys the organ that most determines survival [4].

What are the symptoms of AA amyloidosis?

Because AA amyloidosis typically follows many years of active inflammatory disease, early symptoms are easy to mistake for the underlying illness itself. The first warning signs usually come from the kidneys [3].

Symptoms associated with AA amyloidosis include [1]:

Symptom	What it signals
Swollen feet and legs	Kidney problems / chronic kidney disease
Foamy or frothy urine	Protein leaking into urine (proteinuria)
Peeing less than usual	Declining kidney function
Chronic diarrhea	Deposits in the stomach and intestines
Enlarged kidney	Amyloid infiltration of the kidney
Enlarged liver	Amyloid infiltration of the liver
Low blood pressure	Autonomic or cardiac effects
Nausea and vomiting	Kidney dysfunction and uremia

Two red flags deserve emphasis. Foamy, frothy urine is the classic early sign of proteinuria, it means the kidneys' filtering units are leaking protein and should prompt testing. And in someone with a long history of rheumatoid arthritis, Crohn's disease, recurrent fevers, or chronic infection, new leg swelling plus frothy urine should raise suspicion for AA amyloidosis specifically [1] [3].

How is AA amyloidosis diagnosed?

There is no blood test that diagnoses AA amyloidosis on its own. The definitive diagnosis requires a tissue biopsy: a small sample of tissue is stained with Congo red dye, and under polarized light microscopy, amyloid deposits glow with a characteristic apple-green birefringence. The biopsy also has to prove the deposits are the AA type (not AL or another form), typically with immunohistochemistry or mass spectrometry typing [1] [2] [3].

In practice, diagnosis often starts with a simple fat pad biopsy, a needle sample of abdominal fat just under the skin, and may be followed by an organ biopsy of the affected tissue (kidney, liver, or other) if the fat pad is negative [1].

The diagnostic sequence generally follows these steps:

1. Clinical suspicion: proteinuria or kidney dysfunction in someone with long-standing inflammatory disease, plus persistently elevated SAA levels.

2. Blood and urine tests: serum creatinine, estimated GFR, 24-hour proteinuria, serum albumin, and SAA concentration.

3. Fat pad biopsy with Congo red staining.

4. Organ biopsy if needed (kidney is most informative).

5. Typing the amyloid to confirm the AA subtype and rule out AL amyloidosis, which looks similar but behaves more aggressively [1] [2] [3].

Ruling out AL amyloidosis matters because the two are treated very differently, AL requires urgent blood-cancer-directed therapy, while AA requires inflammation control [1].

Is AA amyloidosis curable, and how is it treated?

Yes, and this is one of the more hopeful features of AA amyloidosis. Because the disease is caused by chronic inflammation, treating the underlying inflammatory condition treats the amyloidosis itself. When the inflammation is brought under control, SAA production falls, new deposits stop forming, and existing organ dysfunction can stabilize and even improve [1] [3].

The treatment strategy has a clear target: bring the SAA concentration down to an ideal goal of less than 10 mg/L, the level at which the risk of disease progression is minimized and organ recovery becomes possible [3].

Treatment approach	How it works	When it applies
Treat the underlying cause (foundation)	Removes the driver of chronic SAA overproduction	Every patient, always
Antimicrobial therapy	Eradicates chronic infections (e.g., chronic ulcers, osteomyelitis)	Infection-driven AA
Colchicine	Prevents attacks of familial Mediterranean fever, the key inherited trigger	FMF-related AA
Immunosuppressive agents / biologics	Suppress autoimmune inflammation (e.g., in rheumatoid arthritis, IBD)	Autoimmune-driven AA
Organ support	Kidney failure managed with dialysis; kidney transplant if underlying disease is controlled	End-stage renal disease
Emerging therapies (in development)	Agents that clear SAA fibrils from the bloodstream and lab-made antibodies that target deposits already in organs	Clinical research

One caution about prognosis and treatment: outcomes depend heavily on how early the diagnosis is made and how well the SAA level can be sustained at low concentrations. Poor prognosis factors include older age, low serum albumin, kidney failure already present at diagnosis, and persistently elevated SAA during follow-up. Patients whose AA amyloidosis is rooted in chronic infection historically had worse outcomes, partly because the underlying infections themselves are harder to control [3].

Survival data has improved substantially. Older studies quoted a median survival of roughly two years, but a large modern cohort of 374 AA amyloidosis patients followed a median survival of 133 months (over 11 years) from diagnosis, reflecting better inflammation control in the modern treatment era [6] [7].

How does AA amyloidosis compare to other types?

Feature	AA amyloidosis	AL amyloidosis (most common type in the West)
Misfolded protein	Serum amyloid A (SAA)	Immunoglobulin light chains
Root cause	Chronic inflammation	Plasma cell disorder (blood cancer family)
Dominant organ	Kidneys (~100% involved)	Heart and kidneys
Rarity	Develops in <5% of chronic inflammation patients	About 12 per million per year in the U.S.
Treatment target	Control underlying inflammation (SAA <10 mg/L)	Chemotherapy / stem-cell transplant to kill light-chain-producing cells
Prognosis (modern data)	Median survival 133 months in one large recent cohort	Generally shorter; more aggressive course

The distinction matters: the same biopsy-and-stain test identifies which type you have, and the wrong treatment for either type is a dangerous mistake.

What increases the risk of developing AA amyloidosis?

Several factors stack the odds. First, the underlying disease itself: AA amyloidosis occurs in about 1 to 5% of patients with rheumatoid arthritis, juvenile idiopathic arthritis, and Crohn's disease, and more frequently in lifelong autoinflammatory conditions such as familial Mediterranean fever [4]. Second, time: the median duration of inflammation before an AA amyloidosis diagnosis is about 20 years, meaning long-unchallenged inflammation is the main risk amplifier [4]. Third, geography and era: the disease is more common in Finland, Japan, Turkey, and the Middle East, and in regions where chronic infections (tuberculosis, leprosy, chronic osteomyelitis) remain poorly controlled [3] [2].

Genetics also play a role, specific variants (alleles) of the SAA gene affect how readily the protein turns into amyloid. Ethnic differences are documented: certain SAA1 alleles raise risk in Caucasian rheumatoid arthritis patients, while other variants are linked to faster progression in Japanese patients [2].

When should you see a doctor about possible AA amyloidosis?

If you live with a chronic inflammatory condition, rheumatoid arthritis, juvenile idiopathic arthritis, Crohn's disease or ulcerative colitis, FMF or another periodic fever syndrome, or a chronic infection, and you develop any of the kidney warning signs (leg or foot swelling, foamy urine, reduced urine output) or unexplained chronic diarrhea, see a doctor promptly and mention both the symptoms and your inflammatory disease history. A simple urine protein test and kidney function panel are fast first steps.

Seek urgent care if you develop sudden breathlessness, chest pain, confusion, markedly reduced urination, or severe vomiting, these can signal rapid kidney or heart decompensation.

The bottom line

AA amyloidosis is a rare but serious complication of chronic inflammation in which misfolded serum amyloid A protein deposits on organs, kidneys above all. Fewer than 5% of people with chronic inflammatory disease ever develop it, and it usually takes many years of active inflammation to get there. But unlike several other amyloidosis types, its root cause is treatable: controlling the underlying inflammation lowers SAA, halts new deposits, and can let damaged organs recover. That is why early recognition of the kidney warning signs, foamy urine, swelling, reduced urination, in anyone with long-standing inflammation is so important.

Talk to your doctor if you have a chronic inflammatory condition and any new kidney symptoms. Ask how your condition might relate to AA amyloidosis, and whether regular urine protein and kidney function checks belong in your routine care. Early diagnosis changes the entire trajectory of this disease.

FAQ: AA Amyloidosis

What is AA amyloidosis in simple terms?

AA amyloidosis is a rare disease where chronic inflammation causes the protein serum amyloid A to misfold and build up as sticky deposits on organs, most often the kidneys. It is a complication of long-standing inflammatory diseases like rheumatoid arthritis, Crohn's disease, chronic infections, and inherited fever syndromes.

Is AA amyloidosis curable?

It is treatable, and in many cases effectively controlled. Because the disease is driven by ongoing inflammation, treating the underlying condition stops new amyloid deposits from forming and can allow damaged organs, especially kidneys, to recover. Early diagnosis and treatment is key.

How rare is AA amyloidosis?

Very rare. It develops in fewer than 5% of patients with chronic inflammatory disorders, and roughly a quarter of cases have no clearly identifiable underlying cause. It is more common in Finland, Japan, Turkey, and the Middle East.

Which organs does AA amyloidosis damage?

The kidneys are affected in virtually all cases and drive the symptoms, proteinuria (foamy urine), swelling, and kidney failure. The liver and spleen enlarge, the gut causes chronic diarrhea, and clinically significant heart involvement is rare (about 5%).

What are the first symptoms of AA amyloidosis?

Swollen feet and legs, foamy or frothy urine, and peeing less than usual are the earliest kidney signals. Chronic diarrhea, enlarged liver or kidneys, low blood pressure, nausea, and vomiting also occur as the disease progresses.

How is AA amyloidosis diagnosed?

Through a tissue biopsy, usually a fat pad sample under the skin, sometimes a kidney biopsy. The tissue is stained with Congo red dye; amyloid deposits show apple-green birefringence under polarized light. The biopsy must also confirm the AA type to rule out AL amyloidosis, which needs different treatment.

What is the treatment for AA amyloidosis?

Treatment targets the root cause: controlling the underlying inflammatory disease with antimicrobials (for chronic infections), colchicine (for familial Mediterranean fever), or immunosuppressants/biologics (for autoimmune diseases). The goal is to lower SAA protein to below 10 mg/L. Kidney failure may require dialysis or, if inflammation is controlled, a transplant.

What is the life expectancy with AA amyloidosis?

Untreated disease can be terminal, with kidney failure causing death in 40 to 60% of cases. However, modern data are encouraging: a large recent cohort of AA amyloidosis patients had a median survival of 133 months (over 11 years) from diagnosis, showing that controlling the underlying inflammation transforms the outlook.

References

1. Cleveland Clinic. AA Amyloidosis: Symptoms, Prognosis & Treatment. Medically reviewed; last updated June 23, 2022.

2. Real de Asúa D, Costa R, Galván JM, et al. Systemic AA amyloidosis: epidemiology, diagnosis, and management. Clinical Epidemiology. 2014;6:369-377.

3. Orphanet. AA amyloidosis. Expert-reviewed, last updated September 2021.

4. Hawkins P. Reactive systemic amyloidosis, AA amyloidosis. In: Rheumatology (Sixth Edition), 2015; summarized at ScienceDirect.

5. Attieh RM, et al. Favorable Outcomes following Kidney Transplant in AA Amyloidosis. Kidney News, vol. 16, no. 3.

6. Gurung R, et al. Renal Amyloidosis: Presentation, Diagnosis, and Management. The American Journal of Medicine. 2022.

7. Ahbap E, et al. Outcome of 121 patients with renal amyloid A amyloidosis. Clinical Rheumatology / PMC. 2014.

8. Bustamante JG, Zaidi SRH. Amyloidosis. StatPearls. Updated February 9, 2022.

9. Brunger AF, Nienhuis HLA, Bijzet J, et al. Causes of AA amyloidosis: a systematic review. Amyloid. 2020;27(1):1-12.

10. García-Pavía P, Rapezzi C, et al. Amyloidosis. Also a Heart Disease. Revista Española de Cardiología. 2011.