By Dr Ananya Mandal, MD
Amyloidosis is a challenging condition to diagnose due to the varying and generalized symptoms it presents with. In addition, amyloid proteins can take years to build up in an organ or tissue before they actually cause symptoms, which may only start to appear when organs are severely damaged. For example, a patient may present with symptoms of kidney failure before amyloidosis in the kidneys is suspected and diagnosed.
If amyloidosis is suspected, a biopsy may be taken form the abdominal fat. However, an abdominal fat biopsy is often not sensitive enough and a biopsy sample of the actual organ or tissue affected may be required. For this procedure, the sample is fixed onto a glass slide and stained with a dye called Congo red dye. Under the polarizing microscope, the stained amyloid protein appears apple green in color. This is called apple-green birefringence.
Once the amyloidosis is confirmed by biopsy, the type of amyloidosis is determined. The different types of amyloidosis are classified according to the type of protein involved and the underlying pathology:
Primary amyloidosis or AL amyloidosis
Primary amyloidosis accounts for around 80% of cases and is caused by immunoglobulin light chains. This condition is associated with plasma cell dyscrasia or cancer of the plasma cells.
Secondary amyloidosis or AA amyloidosis
This form of the condition accounts for around 3% of cases and is caused by an acute phase protein called serum amyloid A. This condition is associated with chronic inflammation, as seen in conditions such as rheumatoid arthritis or inflammatory bowel disease.
This refers to cases of amyloidosis caused by an inherited mutation of the proteins that form fibrils. Usually, the protein involved is the thyroid hormone-binding protein transthyretin.
This amyloidosis is caused by long-term dialysis and affects patient who have been using the treatment for around 8 to 12 years and rarely less than 5 years.
Reviewed by Sally Robertson, BSc
Last Updated: Feb 27, 2014