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) The most common symptoms or side effects of AA amyloidosis are: (2)
Kidney problemsHigh cholesterolSwelling of the ankles or legsEnlarged liver, spleen, or thyroidDiarrhea and constipationHeart fluttering or irregular heartbeat
RELATED: How Doctors Diagnose Amyloidosis 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) 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) 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) RELATED: Everything You Need to Know About High Blood Pressure 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.
