Diagnosis of AA amyloidosis

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Suspicion of AA amyloidosis usually arises if a patient with a longstanding inflammatory condition develops symptoms of kidney disease, often with an enlarged spleen.

The longer that inflammation persists, the greater the chances that AA amyloidosis will appear. The average duration of chronic inflammatory disease before AA amyloidosis appears is about 20 years. However, some patients develop AA amyloidosis after just a few years.

AA amyloid may be widely distributed in the body without causing symptoms. There are always deposits in the spleen, which may be enlarged, but patients usually come to medical attention because of abnormalities in kidney function:

In more than 90% of cases, proteinuria (protein in the urine) is the first sign.  Patients may also have:

1. nephrotic syndrome:

  • large amounts of protein in the urine (>3.5g/day)
  • low albumin in the blood
  • peripheral oedema- swollen ankles

2. end stage kidney failure: the kidneys stop functioning altogether and the patient needs either dialysis or a kidney transplant in order to survive.

3. rarely:

  • haematuria (blood in the urine)
  • renal tubular defects
  • nephrogenic diabetes insipidus
  • renal calcification (calcium deposits in the kidneys)

AA Amyloid deposits leading to illness may also occur, rarely, in the:

  • thyroid gland (goitre)
  • liver (enlarged liver)

There may be AA amyloid deposits in the heart and the gut but these usually do not cause any symptoms.

The diagnosis of amyloidosis may be confirmed (or may be eliminated) by taking a biopsy from the kidney, and/ or undergoing an SAP scan.

Blood tests

Blood tests at the National Amyloidosis Centre

In AA amyloidosis, blood tests may show that the kidneys are not functioning well.
Blood levels of markers of inflammation, known as SAA (serum amyloid A protein)  and CRP (C-reactive protein), are usually raised in AA amyloidosis.The aim of treatment of AA amyloidosis is to control the underlying inflammatory disease and thereby reduce the level of SAA in the blood.

Doctors at the NAC recommend monthly monitoring of SAA levels in the blood in order to guide treatment. When necessary, patients are provided with blood test bottles so their local doctors can draw blood monthly, and the patient can then send the samples to the NAC by post for laboratory testing.

Urine tests

In AA amyloidosis, urine tests may detect:

  • abnormally high levels of protein in the urine
  • blood in the urine (this may be visible only when urine is examined under the microscope)

ECG and Echocardiogram (tests that assess the heart) 

It is very rare for AA amyloidosis to affect the heart, so these are usually normal, unless there is another disease affecting the heart.

Bone marrow examination

AA amyloidosis does not affect the bone marrow, so this test is usually not necessary. If performed, it is usually normal, unless there is another disease affecting the bone marrow. 

Tissue biopsy

Biopsy is a procedure where a small sample of tissue is obtained, processed and examined under the microscope.  More details about tissue biopsy are available here.

SAP scan

SAP scanning shows the distribution and amount of amyloid in the organs throughout the body. SAP scanning has revolutionised understanding of the natural course of amyloidosis and its response to treatment. More details about the SAP scan are available here.

 

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