Like other forms of amyloidosis, AA amyloidosis is a rare disease that involves the buildup of abnormal proteins in the body. But unlike some other forms of amyloidosis, AA shows up as a reaction to another underlying illness. (1) It nearly always affects patients who have rheumatoid arthritis, inflammatory bowel diseases (like Crohn’s disease and ulcerative colitis), tuberculosis, or other types of long-term infection or inflammation. In these disorders, high levels of a protein called serum amyloid protein A (SAA) accumulate and remain in the bloodstream and eventually cause damage to organs.
Other Chronic Conditions or Long-Term Infections Are the Main Causes of AA Amyloidosis
In most cases, AA amyloidosis starts in the liver. In response to infection or inflammation, the liver produces high levels of SAA. These SAA proteins help carry immune cells to inflamed parts of the body. After SAA proteins have performed their duties, the body breaks them down or recycles them.
But if the blood levels of these SAA proteins remain high for a long period of time, sometimes a chunk of them will break away. This broken-off portion is known as amyloid A, or AA. And unlike complete SAA proteins, AA proteins do not naturally break down or decompose in the body. Instead, they form amyloid, the damaging clusters of abnormal proteins that can disrupt normal organ or nerve function. (2)
AA amyloidosis is estimated to account for 18 percent of all amyloidosis cases, making it the second most common type of the disease (after AL amyloidosis), according to a 2016 review. (3) For this reason, it used to be called “secondary” amyloidosis, according to a 2014 review. (4) It was also once called “inflammatory amyloidosis” because it stems from inflammatory conditions. But neither of these terms is used today.
It’s not clear exactly how many people are diagnosed with AA amyloidosis each year, but the disease is more common in developing countries than in the United States or Western Europe. (3) While it nearly always turns up in adults — the average age at diagnosis is 46 years old — AA amyloidosis is one of the only types of the disease that sometimes shows up in children. (2,5)
Doctors don’t know for sure why the SAA protein breaks apart and creates damaging amyloid buildup in patients with AA amyloidosis. Tens of millions of people worldwide suffer from chronic infection or inflammatory diseases. But by some estimates, AA amyloidosis affects one out of a million people. Depending on causing illness, rates of AA amyloidosis can vary widely: The prevalence of AA amyloidosis in those with rheumatoid arthritis, is estimated to be 5 to 78 percent, and in those with familial Mediterranean fever, it’s estimated to be 9 to 13 percent. (4,6)
What Are the Symptoms of AA Amyloidosis?
Like AL amyloidosis, AA amyloidosis is considered a systemic disease, meaning it can turn up in many different parts of the body — and therefore causes a wide range of symptoms. Some of these symptoms are more common than others. But they all are considered nonspecific, because they are usually caused by other, more common medical conditions. (2)
The most common symptoms or side effects of AA amyloidosis are: (2)
- Kidney problems
- High cholesterol
- Swelling of the ankles or legs
- Enlarged liver, spleen, or thyroid
- Diarrhea and constipation
- Heart fluttering or irregular heartbeat
What’s the Typical Prognosis, and Is AA Amyloidosis Deadly?
AA amyloidosis can be deadly, but it’s not a speedy killer. Patients who are diagnosed with the disease live for an average of 11 years following diagnosis, according to a 2007 study, and even longer with recent advancements in treatment and diagnosis. (7)
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Doctors tend to make a diagnosis of AA amyloidosis based on urine or blood tests. For example, if a patient has a chronic infection and a urine test shows elevated levels of AA protein, follow-up tests (including liver or kidney biopsies) can confirm that a patient has AA amyloidosis. (2)
RELATED: What Your Urine Says About You and Your Health
Unlike other forms of amyloidosis, AA amyloidosis does not typically lead to a life-threatening buildup of amyloid in the heart. Instead, the buildup is most common in the patient’s kidneys. Over time, this buildup can lead to kidney failure, and potentially even death. (2)
How Is AA Amyloidosis Treated?
To treat AA amyloidosis, doctors usually start by prescribing drugs or therapies to manage the underlying infection or source of inflammation. (2) For example, if a patient has rheumatoid arthritis, anti-inflammatory drugs may be an effective way to manage that condition, and that treatment may also slow the body’s production of amyloid proteins.
RELATED: Treatments That Help Rheumatoid Arthritis
There are also drugs that effectively slow or stop the accumulation of amyloid, such as tocilizumab (Actemra) and dimethyl sulfoxide (Rimso-50). Kidney transplants and other procedures may be life-saving remedies for some AA patients who are suffering from organ failure as a result of amyloid buildup. (1)
How Does AA Amyloidosis Harm the Kidneys?
In patients with AA amyloidosis, the buildup of amyloid proteins tends to happen in the kidneys, which are the organs that help scrub the blood of waste or toxins. As these amyloid proteins accumulate, patients may develop something known as nephrotic syndrome. (2)
Nephrotic syndrome is an umbrella term for a cluster of symptoms that occur as a result of poor kidney function. These symptoms include elevated blood pressure, fatigue, unexplained weight gain, and foamy urine. (2)
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For patients with nephrotic syndrome, a diet low in protein and salt can lighten the kidney’s workload, and therefore help ease or relieve many of these symptoms. (2)
But it’s worth reiterating that AA amyloidosis is an incredibly rare disease — especially in the U.S. If you’re dealing with many of these symptoms, you should consult your doctor even though the odds are very small that AA amyloidosis is to blame.