Amyloidosis - Diagnosis

Diagnosis

If diagnosis of amyloidosis is suspected, a tissue sample of abdominal wall fat, the rectum or a salivary gland, can be examined in biopsy for evidence of characteristic amyloid deposits.

The tissue is treated with various stains. The most useful stain in the diagnosis of amyloid is Congo red, which, combined with polarized light, makes the amyloid proteins appear apple-green on microscopy. Alternatively, thioflavin T stain may be used. An abdominal wall fat biopsy is not completely sensitive and, sometimes, biopsy of an involved organ (such as the kidney) is required to achieve a diagnosis.

The nature of the amyloid protein can be determined by various ways: the detection of abnormal proteins in the bloodstream (on protein electrophoresis or light chain determination), binding of particular antibodies to the amyloid found in the tissue, or extraction of the protein and identification of its individual amino acids.

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