Amyloidosis

Amyloidosis is a condition involving the deposition of insoluble proteins within various tissues and organs of the body.
When certain protein monomers unravel into characteristic beta-pleated ribbon structures, partially denatured monomers are formed. These aberrantly folded proteins can act as seeds for recruiting additional monomers and triggering oligomerization. The resulting prefibrilar oligomers continue to elongate, eventually forming mature amyloid fibrils.
These amyloid fibrils are insoluble and can accumulate throughout the body, affecting one or more organs. As a result, the symptoms of amyloidosis depend upon which organs are involved and can be quite variable. In fact, the diagnosis of amyloidosis often starts with the detection of high protein levels in the urine. For proper diagnosis, however, an abdominal fat pad biopsy must be analyzed.
Amyloid proteins in the fat pad biopsy stained with Congo Red dye produce apple-green birefringence under polarized light, allowing for a confirmation of amyloidosis.
In the case of primary, or acute light-chain (AL) amyloidosis, the amyloid protein is derived from kappa or lambda immunoglobulin light chain molecules.
This can be positively identified by serum or urine protein electrophoresis to detect the presence of an M-spike. To further characterize the nature of the aberrant immunoglobulin, immunofixation is generally used to demonstrate whether the monoclonal gammopathy is derived from kappa or lambda light chains.